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/obj/Debug/net10.0/QuantEngine.Web.AssemblyInfo.cs

@@ -0,0 +1,22 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+using System;
+using System.Reflection;
+
+[assembly: System.Reflection.AssemblyCompanyAttribute("QuantEngine.Web")]
+[assembly: System.Reflection.AssemblyConfigurationAttribute("Debug")]
+[assembly: System.Reflection.AssemblyFileVersionAttribute("1.0.0.0")]
+[assembly: System.Reflection.AssemblyInformationalVersionAttribute("1.0.0+4ef7a54ad55182e164ca78e8af21f2a5e214c98f")]
+[assembly: System.Reflection.AssemblyProductAttribute("QuantEngine.Web")]
+[assembly: System.Reflection.AssemblyTitleAttribute("QuantEngine.Web")]
+[assembly: System.Reflection.AssemblyVersionAttribute("1.0.0.0")]
+
+// Generated by the MSBuild WriteCodeFragment class.
+