feat(collection): PostgreSQL 백킹 활성화 (CollectionRepository + TokenCache)

- Program.cs: PlaceholderCollectionRepository/TokenCache/KisApiClient → 실제 구현체로 변경
- 데이터베이스 초기화: EnsureTablesAsync() 호출 (시작 시 테이블 자동 생성)
- kis_tokens, kis_collection_runs, kis_collection_snapshots, kis_collection_errors 테이블
- Dapper 기반 SQL 쿼리 (파라미터화, SQL 주입 방지)
- 인덱스: started_at, ticker, captured_at, run_id
- PlaceholderImplementations.cs 제거

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

src/dotnet/QuantEngine.Web/Program.cs

@@ -37,10 +37,10 @@ builder.Services.AddScoped<IPostgresqlHistoryStore, PostgresqlHistoryStore>();
 builder.Services.AddScoped<IPostgresqlHistorySnapshotReader, PostgresqlHistorySnapshotReader>();
 builder.Services.AddScoped<HistoryIngestionService>();
 
-// Collection Pipeline Services (using placeholder implementations for now)
-builder.Services.AddScoped<ICollectionRepository, PlaceholderCollectionRepository>();
-builder.Services.AddScoped<ITokenCache, PlaceholderTokenCache>();
-builder.Services.AddScoped<IKisApiClient, PlaceholderKisApiClient>();
+// Collection Pipeline Services (PostgreSQL-backed implementations)
+builder.Services.AddScoped<ICollectionRepository, CollectionRepository>();
+builder.Services.AddScoped<ITokenCache, PostgresTokenCache>();
+builder.Services.AddScoped<IKisApiClient, KisApiClient>();
 
 // HTTP Client & API Services
 builder.Services.AddHttpClient<ApiClient>();
@@ -48,6 +48,25 @@ builder.Services.AddScoped<ApiClient>();
 
 var app = builder.Build();
 
+// Initialize database tables (PostgreSQL-backed repositories)
+using (var scope = app.Services.CreateScope())
+{
+    var tokenCache = scope.ServiceProvider.GetRequiredService<ITokenCache>();
+    var collectionRepo = scope.ServiceProvider.GetRequiredService<ICollectionRepository>();
+
+    try
+    {
+        // Ensure tables exist on startup
+        await tokenCache.GetCachedTokenAsync("_init_test_");
+        await collectionRepo.GetDashboardStateAsync();
+        Log.Information("Database tables initialized successfully");
+    }
+    catch (Exception ex)
+    {
+        Log.Warning($"Database initialization warning: {ex.Message}");
+    }
+}
+
 // Enable reverse proxy subpath mapping
 app.UsePathBase("/quant");