feat: standalone Blazor WebAssembly admin + SEO enhancements

Architecture:
- Admin UI: /admin (Standalone Blazor WebAssembly, 219 WASM files)
- Portal: /portal (Razor Pages, Cookie/OAuth auth)
- Homepage: / (Razor Pages, SSR)
- API: /api (FastEndpoints + JWT)

SEO:
- Sitemap: Public content only (blog, FAQ, announcements, contact)
- robots.txt: Exclude /admin and /portal, reference production domain
- Naver verification: naverb1813cd79ddc2ded5c5291fca5cb46c2.html ready

Technical:
- TaxBaik.Web.Client: StaticWebAssetBasePath=admin
- Server Program.cs: UseBlazorFrameworkFiles + MapFallback for SPA routing
- base href="/admin/" for client-side navigation
- blazor.webassembly.js (standalone, not web.js)

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

src/TaxBaik.Web.Client/Components/Admin/Services/BlogBrowserClient.cs

@@ -0,0 +1,104 @@
+namespace TaxBaik.Web.Client.Components.Admin.Services;
+
+using System.Net.Http.Json;
+using TaxBaik.Application.DTOs;
+
+public interface IBlogBrowserClient
+{
+    Task<(IEnumerable<BlogPostResponseDto> Items, int Total)> GetAdminPagedAsync(int page = 1, int pageSize = 20, CancellationToken ct = default);
+    Task<(IEnumerable<BlogPostResponseDto> Items, int Total)> GetArchivedPagedAsync(int page = 1, int pageSize = 20, CancellationToken ct = default);
+    Task<BlogPostResponseDto?> GetByIdAsync(int id, CancellationToken ct = default);
+    Task<BlogPostResponseDto?> CreateAsync(CreateBlogPostDto dto, CancellationToken ct = default);
+    Task<BlogPostResponseDto?> UpdateAsync(int id, CreateBlogPostDto dto, CancellationToken ct = default);
+    Task<bool> DeleteAsync(int id, CancellationToken ct = default);
+    Task<bool> RestoreAsync(int id, CancellationToken ct = default);
+    Task<bool> TogglePublishAsync(int id, CreateBlogPostDto dto, CancellationToken ct = default);
+}
+
+public class BlogBrowserClient : IBlogBrowserClient
+{
+    private readonly HttpClient _http;
+    private readonly ILogger<BlogBrowserClient> _logger;
+    private readonly ITokenStore _tokenStore;
+
+    public BlogBrowserClient(HttpClient http, ILogger<BlogBrowserClient> logger, ITokenStore tokenStore)
+    {
+        _http = http;
+        _logger = logger;
+        _tokenStore = tokenStore;
+    }
+
+    private void EnsureAuthHeader()
+    {
+        if (!string.IsNullOrEmpty(_tokenStore.AccessToken))
+            _http.DefaultRequestHeaders.Authorization = new("Bearer", _tokenStore.AccessToken);
+        else
+            _http.DefaultRequestHeaders.Authorization = null;
+    }
+
+    public async Task<(IEnumerable<BlogPostResponseDto> Items, int Total)> GetAdminPagedAsync(int page = 1, int pageSize = 20, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var result = await _http.GetFromJsonAsync<PagedResponse>($"blog/admin?page={page}&pageSize={pageSize}", ct);
+        return result != null ? (result.Data, result.Total) : ([], 0);
+    }
+
+    public async Task<(IEnumerable<BlogPostResponseDto> Items, int Total)> GetArchivedPagedAsync(int page = 1, int pageSize = 20, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var result = await _http.GetFromJsonAsync<PagedResponse>($"blog/admin/archived?page={page}&pageSize={pageSize}", ct);
+        return result != null ? (result.Data, result.Total) : ([], 0);
+    }
+
+    public async Task<BlogPostResponseDto?> GetByIdAsync(int id, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        return await _http.GetFromJsonAsync<BlogPostResponseDto>($"blog/{id}", ct);
+    }
+
+    public async Task<BlogPostResponseDto?> CreateAsync(CreateBlogPostDto dto, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var response = await _http.PostAsJsonAsync("blog", dto, ct);
+        if (!response.IsSuccessStatusCode)
+            return null;
+        var content = await response.Content.ReadAsStringAsync(ct);
+        return System.Text.Json.JsonSerializer.Deserialize<BlogPostResponseDto>(content, new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+    }
+
+    public async Task<BlogPostResponseDto?> UpdateAsync(int id, CreateBlogPostDto dto, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var response = await _http.PutAsJsonAsync($"blog/{id}", dto, ct);
+        if (!response.IsSuccessStatusCode)
+            return null;
+        var content = await response.Content.ReadAsStringAsync(ct);
+        return System.Text.Json.JsonSerializer.Deserialize<BlogPostResponseDto>(content, new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+    }
+
+    public async Task<bool> DeleteAsync(int id, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var response = await _http.DeleteAsync($"blog/{id}", ct);
+        return response.IsSuccessStatusCode;
+    }
+
+    public async Task<bool> RestoreAsync(int id, CancellationToken ct = default)
+    {
+        EnsureAuthHeader();
+        var response = await _http.PostAsync($"blog/{id}/restore", null, ct);
+        return response.IsSuccessStatusCode;
+    }
+
+    public async Task<bool> TogglePublishAsync(int id, CreateBlogPostDto dto, CancellationToken ct = default)
+    {
+        var result = await UpdateAsync(id, dto, ct);
+        return result != null;
+    }
+
+    private sealed class PagedResponse
+    {
+        public List<BlogPostResponseDto> Data { get; set; } = [];
+        public int Total { get; set; }
+    }
+}