Add game version management system with manifest support

Features:
- Version dropdown in single/ZIP upload (9.3.0, 9.2.0, etc.)
- Patch-compatible matching (9.3.x assets work with 9.3.0)
- manifest.json/xml support for automatic metadata detection
- Smart category auto-detection from folder structure
- Version field stored in GameAssets table

Manifest support:
- JSON format with gameVersion, category, assets array
- Per-file metadata overrides (type, required, description)
- Auto-detect falls back if no manifest present
- See ASSET-MANIFEST-SPECIFICATION.md for full spec

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

RR3CommunityServer/Program.cs

@@ -38,6 +38,9 @@ builder.Services.AddScoped<IDrmService, DrmService>();
 builder.Services.AddScoped<IAuthService, AuthService>();
 builder.Services.AddScoped<AssetExtractionService>();
 
+// Add HttpClient for URL downloads
+builder.Services.AddHttpClient();
+
 // CORS for cross-origin requests
 builder.Services.AddCors(options =>
 {