feat: Migrate admin UI from Blazor WASM/MudBlazor to Razor Pages/Cookie Auth/Tabler

- Remove QuantEngine.Web.Client from .sln (keep on disk for reference)
- Replace Blazor Interactive WebAssembly with server-rendered Razor Pages
- Implement Cookie Authentication (HttpOnly, SameSite=Lax, 12h expiry)
- Add AuthService with BCrypt password hashing + auto-migration from SHA-256
- Implement IpLockoutService (3 strikes → 15-min ban)
- Create Admin folder structure with Layout + shared partials
- Implement Dashboard, Collection, Users index pages (base structure)
- Remove hardcoded backdoors (master_recovery, dev auth bypass)
- Remove hardcoded localhost:5265 URLs
- Add Tabler UI base styling (Bootstrap 5 CDN + custom admin.css)
- Update CLAUDE.md with new UI standards and auth policies
- Build: 0 errors, 0 warnings (ready for dev testing)

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

src/dotnet/QuantEngine.Web/Pages/Admin/Collection/Index.cshtml.cs

@@ -0,0 +1,35 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using QuantEngine.Core.Interfaces;
+using QuantEngine.Web.Services;
+
+namespace QuantEngine.Web.Pages.Admin.Collection;
+
+[Authorize(AuthenticationSchemes = AdminAuthDefaults.Scheme)]
+public class IndexModel : PageModel
+{
+    private readonly ICollectionRepository _collectionRepository;
+    private readonly ILogger<IndexModel> _logger;
+
+    public List<CollectionRunRecord>? Runs { get; set; }
+    public string? Message { get; set; }
+
+    public IndexModel(ICollectionRepository collectionRepository, ILogger<IndexModel> logger)
+    {
+        _collectionRepository = collectionRepository;
+        _logger = logger;
+    }
+
+    public async Task OnGetAsync()
+    {
+        try
+        {
+            Runs = await _collectionRepository.GetRecentRunsAsync(limit: 20);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Collection runs loading failed");
+            Message = "데이터 수집 현황을 불러올 수 없습니다.";
+        }
+    }
+}