fix: 로그인 HTTP 자기호출 완전 제거 — IWorkspaceRepository 직접 DI 주입

이전 수정(34df08d)에서 localhost:5265로 고정했으나,
프로덕션 서버는 포트 5000으로 실행 중이어서 Connection refused 발생.

근본 원인: Razor 로그인 페이지가 자기 자신의 API를 HTTP로 재호출하는 구조.

해결:
- HttpClient 자기호출 완전 제거
- IWorkspaceRepository를 Razor 페이지에 직접 DI 주입
- DB 조회 → SHA-256 해시 검증 → 세션 발급 → 쿠키 설정을 인라인 처리
- 포트/프록시 의존성 완전 제거

src/dotnet/QuantEngine.Web/Pages/Account/Login.cshtml.cs

@@ -1,22 +1,26 @@
+using System.Security.Cryptography;
+using System.Text;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
+using QuantEngine.Core.Interfaces;
+using QuantEngine.Core.Models;
 
 namespace QuantEngine.Web.Pages.Account
 {
     [AllowAnonymous]
     public class LoginModel : PageModel
     {
-        private readonly HttpClient _httpClient;
+        private readonly IWorkspaceRepository _workspaceRepo;
         private readonly ILogger<LoginModel> _logger;
 
         public string? Username { get; set; }
         public bool RememberUsername { get; set; }
         public string? ErrorMessage { get; set; }
 
-        public LoginModel(HttpClient httpClient, ILogger<LoginModel> logger)
+        public LoginModel(IWorkspaceRepository workspaceRepo, ILogger<LoginModel> logger)
         {
-            _httpClient = httpClient;
+            _workspaceRepo = workspaceRepo;
             _logger = logger;
         }
 
@@ -41,51 +45,89 @@ namespace QuantEngine.Web.Pages.Account
 
             try
             {
-                var loginRequest = new { Username = username, Password = password };
-                // Always call the internal API directly to avoid Cloudflare proxy interference.
-                // Request.Host / Request.Scheme must NOT be used here — they resolve to the external
-                // domain which causes the self-call to go out through Cloudflare and return 400.
-                var requestUri = "http://localhost:5265/api/auth/login";
-                var response = await _httpClient.PostAsJsonAsync(requestUri, loginRequest);
-
-                if (response.IsSuccessStatusCode)
+                // Direct repository call — no internal HTTP round-trip.
+                // Using IWorkspaceRepository injected via DI avoids any port/proxy dependency.
+                WorkspaceAccount? account = null;
+                try
                 {
-                    // Extract set-cookie header from API response and set it on proxy client response
-                    if (response.Headers.TryGetValues("Set-Cookie", out var cookieHeaders))
-                    {
-                        foreach (var cookieHeader in cookieHeaders)
-                        {
-                            Response.Headers.Append("Set-Cookie", cookieHeader);
-                        }
-                    }
-
-                    if (rememberUsername)
-                    {
-                        Response.Cookies.Append(
-                            "quant_admin_username",
-                            username,
-                            new Microsoft.AspNetCore.Http.CookieOptions
-                            {
-                                Expires = DateTimeOffset.UtcNow.AddDays(30),
-                                HttpOnly = false,
-                                SameSite = Microsoft.AspNetCore.Http.SameSiteMode.Strict
-                            }
-                        );
-                    }
-                    else
-                    {
-                        Response.Cookies.Delete("quant_admin_username");
-                    }
-
-                    return Redirect("/");
+                    account = await _workspaceRepo.GetAccountByUsernameAsync(username.Trim());
                 }
-                else
+                catch (Exception dbEx)
+                {
+                    _logger.LogError(dbEx, "[Login] Database lookup failed for user '{Username}'", username);
+                    ErrorMessage = "데이터베이스 연결 오류가 발생했습니다. 잠시 후 다시 시도해 주세요.";
+                    Username = username;
+                    RememberUsername = rememberUsername;
+                    return Page();
+                }
+
+                if (account is null || !string.Equals(account.IsActive, "true", StringComparison.OrdinalIgnoreCase))
                 {
                     ErrorMessage = "로그인 실패: 아이디 또는 비밀번호가 올바르지 않습니다.";
                     Username = username;
                     RememberUsername = rememberUsername;
                     return Page();
                 }
+
+                var passwordHash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(password)));
+                if (!string.Equals(account.PasswordHash, passwordHash, StringComparison.OrdinalIgnoreCase))
+                {
+                    ErrorMessage = "로그인 실패: 아이디 또는 비밀번호가 올바르지 않습니다.";
+                    Username = username;
+                    RememberUsername = rememberUsername;
+                    return Page();
+                }
+
+                // Issue session token
+                var rawToken = Guid.NewGuid().ToString("N");
+                var tokenHash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(rawToken)));
+                var now = DateTimeOffset.UtcNow;
+                var expiresAt = now.AddDays(7);
+
+                await _workspaceRepo.UpsertSessionAsync(new WorkspaceSession
+                {
+                    SessionTokenHash = tokenHash,
+                    Username = account.Username,
+                    Role = account.Role,
+                    CreatedAt = now.ToString("O"),
+                    ExpiresAt = expiresAt.ToString("O"),
+                    RevokedAt = null
+                });
+
+                // Set HTTP-only auth cookie (Secure=true since production is always HTTPS via Cloudflare)
+                Response.Cookies.Append(
+                    "quant_auth_token",
+                    rawToken,
+                    new Microsoft.AspNetCore.Http.CookieOptions
+                    {
+                        HttpOnly = true,
+                        Secure = true,
+                        SameSite = Microsoft.AspNetCore.Http.SameSiteMode.Lax,
+                        Expires = expiresAt,
+                        Path = "/"
+                    }
+                );
+
+                if (rememberUsername)
+                {
+                    Response.Cookies.Append(
+                        "quant_admin_username",
+                        username,
+                        new Microsoft.AspNetCore.Http.CookieOptions
+                        {
+                            Expires = DateTimeOffset.UtcNow.AddDays(30),
+                            HttpOnly = false,
+                            SameSite = Microsoft.AspNetCore.Http.SameSiteMode.Strict
+                        }
+                    );
+                }
+                else
+                {
+                    Response.Cookies.Delete("quant_admin_username");
+                }
+
+                _logger.LogInformation("[Login] User '{Username}' authenticated successfully", account.Username);
+                return Redirect("/");
             }
             catch (Exception ex)
             {
@@ -99,7 +141,6 @@ namespace QuantEngine.Web.Pages.Account
 
         public IActionResult OnGetLogout()
         {
-            // Revoke cookies securely
             Response.Cookies.Delete("quant_auth_token");
             return Redirect("/Account/Login");
         }