feat: integrate Serilog and Telegram notifications

- Add Serilog for structured logging (Console + File)
- Implement TelegramNotificationService for admin alerts
- Log successful/failed login attempts with Telegram notifications
- Add application startup/shutdown logging
- Log important events to Telegram Chat ID: -5585148480
- Configuration: Telegram:BotToken and Telegram:ChatId in appsettings

Features:
- Automatic daily log rotation
- Structured logging with timestamps
- Environment-aware alerts
- Error and info level Telegram messages

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

TaxBaik.Web/Program.cs

@@ -8,6 +8,7 @@ using Microsoft.AspNetCore.HttpOverrides;
 using Microsoft.AspNetCore.ResponseCompression;
 using Microsoft.IdentityModel.Tokens;
 using MudBlazor.Services;
+using Serilog;
 using TaxBaik.Application;
 using TaxBaik.Application.Services;
 using TaxBaik.Infrastructure;
@@ -16,6 +17,20 @@ using TaxBaik.Web.Services;
 var builder = WebApplication.CreateBuilder(args);
 var isProduction = builder.Environment.IsProduction();
 
+// Serilog 설정
+builder.Host.UseSerilog((context, config) =>
+{
+    config
+        .MinimumLevel.Information()
+        .WriteTo.Console()
+        .WriteTo.File(
+            path: "logs/taxbaik-.log",
+            rollingInterval: RollingInterval.Day,
+            outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz}] [{Level:u3}] {Message:lj}{NewLine}{Exception}")
+        .Enrich.FromLogContext()
+        .Enrich.WithProperty("Environment", context.HostingEnvironment.EnvironmentName);
+});
+
 // Controllers (API)
 builder.Services.AddControllers();
 builder.Services.AddProblemDetails();
@@ -72,6 +87,9 @@ builder.Services.AddAuthorizationCore();
 // Notifications (SignalR)
 builder.Services.AddScoped<INotificationService, NotificationService>();
 
+// Telegram Notification
+builder.Services.AddHttpClient<ITelegramNotificationService, TelegramNotificationService>();
+
 // HTTP Client for API (with automatic token refresh)
 builder.Services.AddScoped<ITokenStore, TokenStore>();
 builder.Services.AddScoped<TokenRefreshHandler>();
@@ -202,4 +220,39 @@ app.MapRazorComponents<TaxBaik.Web.Components.Admin.App>()
    .AddInteractiveServerRenderMode()
    .AllowAnonymous();
 
-app.Run();
+// 애플리케이션 시작/종료 로깅
+try
+{
+    Log.Information("애플리케이션 시작: {Environment}", app.Environment.EnvironmentName);
+    if (!app.Environment.IsDevelopment())
+    {
+        using (var scope = app.Services.CreateScope())
+        {
+            var telegramService = scope.ServiceProvider.GetRequiredService<ITelegramNotificationService>();
+            await telegramService.SendInfoAsync(
+                "서버 시작",
+                $"환경: {app.Environment.EnvironmentName}");
+        }
+    }
+    app.Run();
+}
+catch (Exception ex)
+{
+    Log.Fatal(ex, "애플리케이션 강종");
+    if (!app.Environment.IsDevelopment())
+    {
+        using (var scope = app.Services.CreateScope())
+        {
+            var telegramService = scope.ServiceProvider.GetRequiredService<ITelegramNotificationService>();
+            await telegramService.SendErrorAsync(
+                "서버 오류",
+                $"환경: {app.Environment.EnvironmentName}\n오류: {ex.Message}");
+        }
+    }
+    throw;
+}
+finally
+{
+    Log.Information("애플리케이션 종료");
+    Log.CloseAndFlush();
+}

TaxBaik.Web/Services/AnnouncementBrowserClient.cs

@@ -1,5 +1,6 @@
 namespace TaxBaik.Web.Services;
 
+using System.Net.Http;
 using System.Net.Http.Json;
 using TaxBaik.Application.DTOs;
 using TaxBaik.Domain.Entities;
@@ -17,17 +18,28 @@ public class AnnouncementBrowserClient : IAnnouncementBrowserClient
 {
     private readonly HttpClient _http;
     private readonly ILogger<AnnouncementBrowserClient> _logger;
+    private readonly ITokenStore _tokenStore;
 
-    public AnnouncementBrowserClient(HttpClient http, ILogger<AnnouncementBrowserClient> logger)
+    public AnnouncementBrowserClient(HttpClient http, ILogger<AnnouncementBrowserClient> logger, ITokenStore tokenStore)
     {
         _http = http;
         _logger = logger;
+        _tokenStore = tokenStore;
+    }
+
+    private void EnsureAuthHeader()
+    {
+        if (!string.IsNullOrEmpty(_tokenStore.AccessToken) && !_http.DefaultRequestHeaders.Contains("Authorization"))
+        {
+            _http.DefaultRequestHeaders.Authorization = new("Bearer", _tokenStore.AccessToken);
+        }
     }
 
     public async Task<IEnumerable<Announcement>> GetAllAsync(CancellationToken ct = default)
     {
         try
         {
+            EnsureAuthHeader();
             var result = await _http.GetFromJsonAsync<AnnouncementListResponse>("announcement", cancellationToken: ct);
             return result?.Data ?? [];
         }
@@ -42,6 +54,7 @@ public class AnnouncementBrowserClient : IAnnouncementBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             return await _http.GetFromJsonAsync<Announcement>($"announcement/{id}", cancellationToken: ct);
         }
         catch (HttpRequestException ex)
@@ -55,6 +68,7 @@ public class AnnouncementBrowserClient : IAnnouncementBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PostAsJsonAsync("announcement", dto, cancellationToken: ct);
             if (!response.IsSuccessStatusCode) return null;
 
@@ -74,6 +88,7 @@ public class AnnouncementBrowserClient : IAnnouncementBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PutAsJsonAsync($"announcement/{id}", dto, cancellationToken: ct);
             if (!response.IsSuccessStatusCode) return null;
 
@@ -93,6 +108,7 @@ public class AnnouncementBrowserClient : IAnnouncementBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.DeleteAsync($"announcement/{id}", cancellationToken: ct);
             return response.IsSuccessStatusCode;
         }

TaxBaik.Web/Services/AuthService.cs

@@ -12,15 +12,21 @@ public class AuthService
 {
     private readonly IAdminUserRepository _adminUserRepository;
     private readonly ILogger<AuthService> _logger;
+    private readonly ITelegramNotificationService _telegramService;
     private readonly string _jwtSecretKey;
     private readonly string? _passwordResetToken;
     private readonly int _accessTokenExpirationMinutes = 60;    // Access Token: 1시간 (사용성 향상)
     private readonly int _refreshTokenExpirationMinutes = 10080; // Refresh Token: 7일
 
-    public AuthService(IAdminUserRepository adminUserRepository, ILogger<AuthService> logger, IConfiguration configuration)
+    public AuthService(
+        IAdminUserRepository adminUserRepository,
+        ILogger<AuthService> logger,
+        IConfiguration configuration,
+        ITelegramNotificationService telegramService)
     {
         _adminUserRepository = adminUserRepository;
         _logger = logger;
+        _telegramService = telegramService;
         _jwtSecretKey = configuration["Jwt:SecretKey"] ?? throw new InvalidOperationException("Missing 'Jwt:SecretKey' configuration.");
         _passwordResetToken = configuration["Admin:PasswordResetToken"];
     }
@@ -46,10 +52,16 @@ public class AuthService
         if (!BCrypt.Net.BCrypt.Verify(password, user.PasswordHash))
         {
             _logger.LogWarning("로그인 시도: 잘못된 비밀번호 '{Username}'", username);
+            await _telegramService.SendErrorAsync(
+                "로그인 실패",
+                $"사용자: {username}\n실패 사유: 잘못된 비밀번호");
             return null;
         }
 
         _logger.LogInformation("로그인 성공: {Username}", username);
+        await _telegramService.SendInfoAsync(
+            "관리자 로그인",
+            $"사용자: {username}");
         await _adminUserRepository.UpdateLastLoginAtAsync(user.Id);
         return GenerateTokenPair(user);
     }

TaxBaik.Web/Services/ClientBrowserClient.cs

@@ -1,5 +1,6 @@
 namespace TaxBaik.Web.Services;
 
+using System.Net.Http;
 using System.Net.Http.Json;
 using TaxBaik.Application.DTOs;
 using TaxBaik.Domain.Entities;
@@ -22,11 +23,21 @@ public class ClientBrowserClient : IClientBrowserClient
 {
     private readonly HttpClient _http;
     private readonly ILogger<ClientBrowserClient> _logger;
+    private readonly ITokenStore _tokenStore;
 
-    public ClientBrowserClient(HttpClient http, ILogger<ClientBrowserClient> logger)
+    public ClientBrowserClient(HttpClient http, ILogger<ClientBrowserClient> logger, ITokenStore tokenStore)
     {
         _http = http;
         _logger = logger;
+        _tokenStore = tokenStore;
+    }
+
+    private void EnsureAuthHeader()
+    {
+        if (!string.IsNullOrEmpty(_tokenStore.AccessToken) && !_http.DefaultRequestHeaders.Contains("Authorization"))
+        {
+            _http.DefaultRequestHeaders.Authorization = new("Bearer", _tokenStore.AccessToken);
+        }
     }
 
     public async Task<(IEnumerable<Client> Items, int Total)> GetPagedAsync(
@@ -34,6 +45,7 @@ public class ClientBrowserClient : IClientBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var query = $"client?page={page}&pageSize={pageSize}";
             if (!string.IsNullOrEmpty(status))
                 query += $"&status={status}";
@@ -54,6 +66,7 @@ public class ClientBrowserClient : IClientBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             return await _http.GetFromJsonAsync<Client>($"client/{id}", cancellationToken: ct);
         }
         catch (HttpRequestException ex)
@@ -67,6 +80,7 @@ public class ClientBrowserClient : IClientBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PostAsJsonAsync("client", dto, cancellationToken: ct);
             if (!response.IsSuccessStatusCode)
                 return null;
@@ -87,6 +101,7 @@ public class ClientBrowserClient : IClientBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PutAsJsonAsync($"client/{id}", dto, cancellationToken: ct);
             if (!response.IsSuccessStatusCode)
                 return null;
@@ -107,6 +122,7 @@ public class ClientBrowserClient : IClientBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.DeleteAsync($"client/{id}", cancellationToken: ct);
             return response.IsSuccessStatusCode;
         }

TaxBaik.Web/Services/FaqBrowserClient.cs

@@ -1,5 +1,6 @@
 namespace TaxBaik.Web.Services;
 
+using System.Net.Http;
 using System.Net.Http.Json;
 using TaxBaik.Domain.Entities;
 
@@ -16,17 +17,28 @@ public class FaqBrowserClient : IFaqBrowserClient
 {
     private readonly HttpClient _http;
     private readonly ILogger<FaqBrowserClient> _logger;
+    private readonly ITokenStore _tokenStore;
 
-    public FaqBrowserClient(HttpClient http, ILogger<FaqBrowserClient> logger)
+    public FaqBrowserClient(HttpClient http, ILogger<FaqBrowserClient> logger, ITokenStore tokenStore)
     {
         _http = http;
         _logger = logger;
+        _tokenStore = tokenStore;
+    }
+
+    private void EnsureAuthHeader()
+    {
+        if (!string.IsNullOrEmpty(_tokenStore.AccessToken) && !_http.DefaultRequestHeaders.Contains("Authorization"))
+        {
+            _http.DefaultRequestHeaders.Authorization = new("Bearer", _tokenStore.AccessToken);
+        }
     }
 
     public async Task<IEnumerable<Faq>> GetAllAsync(CancellationToken ct = default)
     {
         try
         {
+            EnsureAuthHeader();
             var result = await _http.GetFromJsonAsync<FaqListResponse>("faq", cancellationToken: ct);
             return result?.Data ?? [];
         }
@@ -41,6 +53,7 @@ public class FaqBrowserClient : IFaqBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             return await _http.GetFromJsonAsync<Faq>($"faq/{id}", cancellationToken: ct);
         }
         catch (HttpRequestException ex)
@@ -54,6 +67,7 @@ public class FaqBrowserClient : IFaqBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PostAsJsonAsync("faq", faq, cancellationToken: ct);
             if (!response.IsSuccessStatusCode) return null;
 
@@ -73,6 +87,7 @@ public class FaqBrowserClient : IFaqBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PutAsJsonAsync($"faq/{id}", faq, cancellationToken: ct);
             if (!response.IsSuccessStatusCode) return null;
 
@@ -92,6 +107,7 @@ public class FaqBrowserClient : IFaqBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.DeleteAsync($"faq/{id}", cancellationToken: ct);
             return response.IsSuccessStatusCode;
         }

TaxBaik.Web/Services/TaxFilingBrowserClient.cs

@@ -1,5 +1,6 @@
 namespace TaxBaik.Web.Services;
 
+using System.Net.Http;
 using System.Net.Http.Json;
 using TaxBaik.Domain.Entities;
 
@@ -20,17 +21,28 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
 {
     private readonly HttpClient _http;
     private readonly ILogger<TaxFilingBrowserClient> _logger;
+    private readonly ITokenStore _tokenStore;
 
-    public TaxFilingBrowserClient(HttpClient http, ILogger<TaxFilingBrowserClient> logger)
+    public TaxFilingBrowserClient(HttpClient http, ILogger<TaxFilingBrowserClient> logger, ITokenStore tokenStore)
     {
         _http = http;
         _logger = logger;
+        _tokenStore = tokenStore;
+    }
+
+    private void EnsureAuthHeader()
+    {
+        if (!string.IsNullOrEmpty(_tokenStore.AccessToken) && !_http.DefaultRequestHeaders.Contains("Authorization"))
+        {
+            _http.DefaultRequestHeaders.Authorization = new("Bearer", _tokenStore.AccessToken);
+        }
     }
 
     public async Task<IEnumerable<TaxFiling>> GetUpcomingAsync(int daysAhead = 30, CancellationToken ct = default)
     {
         try
         {
+            EnsureAuthHeader();
             var result = await _http.GetFromJsonAsync<TaxFilingListResponse>(
                 $"tax-filing/upcoming?daysAhead={daysAhead}", cancellationToken: ct);
             return result?.Data ?? [];
@@ -46,6 +58,7 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var result = await _http.GetFromJsonAsync<TaxFilingListResponse>(
                 $"tax-filing/client/{clientId}", cancellationToken: ct);
             return result?.Data ?? [];
@@ -61,6 +74,7 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             return await _http.GetFromJsonAsync<TaxFiling>(
                 $"tax-filing/{id}", cancellationToken: ct);
         }
@@ -75,6 +89,7 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PostAsJsonAsync("tax-filing", filing, cancellationToken: ct);
             if (!response.IsSuccessStatusCode)
                 return null;
@@ -95,6 +110,7 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.PutAsJsonAsync($"tax-filing/{id}", filing, cancellationToken: ct);
             if (!response.IsSuccessStatusCode)
                 return null;
@@ -115,6 +131,7 @@ public class TaxFilingBrowserClient : ITaxFilingBrowserClient
     {
         try
         {
+            EnsureAuthHeader();
             var response = await _http.DeleteAsync($"tax-filing/{id}", cancellationToken: ct);
             return response.IsSuccessStatusCode;
         }

TaxBaik.Web/Services/TelegramNotificationService.cs

@@ -0,0 +1,76 @@
+namespace TaxBaik.Web.Services;
+
+using System.Net.Http.Json;
+
+/// <summary>
+/// Telegram Bot 알림 서비스
+/// 중요 로깅 및 오류를 Telegram으로 전송
+/// </summary>
+public interface ITelegramNotificationService
+{
+    Task SendMessageAsync(string message, CancellationToken ct = default);
+    Task SendErrorAsync(string title, string details, CancellationToken ct = default);
+    Task SendInfoAsync(string title, string message, CancellationToken ct = default);
+}
+
+public class TelegramNotificationService : ITelegramNotificationService
+{
+    private readonly HttpClient _httpClient;
+    private readonly ILogger<TelegramNotificationService> _logger;
+    private readonly string _botToken;
+    private readonly string _chatId;
+    private const string TelegramApiUrl = "https://api.telegram.org";
+
+    public TelegramNotificationService(
+        HttpClient httpClient,
+        ILogger<TelegramNotificationService> logger,
+        IConfiguration config)
+    {
+        _httpClient = httpClient;
+        _logger = logger;
+        _botToken = config["Telegram:BotToken"] ?? "";
+        _chatId = config["Telegram:ChatId"] ?? "";
+    }
+
+    public async Task SendMessageAsync(string message, CancellationToken ct = default)
+    {
+        if (string.IsNullOrEmpty(_botToken) || string.IsNullOrEmpty(_chatId))
+        {
+            _logger.LogWarning("Telegram credentials not configured");
+            return;
+        }
+
+        try
+        {
+            var url = $"{TelegramApiUrl}/bot{_botToken}/sendMessage";
+            var payload = new
+            {
+                chat_id = _chatId,
+                text = message,
+                parse_mode = "HTML"
+            };
+
+            var response = await _httpClient.PostAsJsonAsync(url, payload, cancellationToken: ct);
+            if (!response.IsSuccessStatusCode)
+            {
+                _logger.LogError("Failed to send Telegram message: {StatusCode}", response.StatusCode);
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error sending Telegram message");
+        }
+    }
+
+    public async Task SendErrorAsync(string title, string details, CancellationToken ct = default)
+    {
+        var message = $"<b>❌ {title}</b>\n\n{details}\n\n<i>{DateTime.UtcNow:yyyy-MM-dd HH:mm:ss} UTC</i>";
+        await SendMessageAsync(message, ct);
+    }
+
+    public async Task SendInfoAsync(string title, string message, CancellationToken ct = default)
+    {
+        var text = $"<b>ℹ️ {title}</b>\n\n{message}\n\n<i>{DateTime.UtcNow:yyyy-MM-dd HH:mm:ss} UTC</i>";
+        await SendMessageAsync(text, ct);
+    }
+}

TaxBaik.Web/TaxBaik.Web.csproj

@@ -17,6 +17,9 @@
     <PackageReference Include="System.IdentityModel.Tokens.Jwt" Version="8.19.1" />
     <PackageReference Include="Microsoft.IdentityModel.Tokens" Version="8.19.1" />
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.9" />
+    <PackageReference Include="Serilog.AspNetCore" Version="8.0.1" />
+    <PackageReference Include="Serilog.Sinks.Console" Version="6.0.0" />
+    <PackageReference Include="Serilog.Sinks.File" Version="5.0.0" />
   </ItemGroup>
 
 </Project>

TaxBaik.Web/appsettings.json

@@ -18,8 +18,8 @@
     "BaseUrl": "http://localhost:5001/taxbaik/api/"
   },
   "Telegram": {
-    "BotToken": "",
-    "ChatId": ""
+    "BotToken": "8679990909:AAGLLRUIAuEbYAZVGOYDu-UuTu4ihroEiX0",
+    "ChatId": "-5585148480"
   },
   "Admin": {
     "PasswordResetToken": "dev-reset-token-12345"