feat(api): add OAuth2Controller (Google authorize/callback), SyncController (on-demand trigger); register IHttpContextAccessor

src/presentation/DigitalData.MessagingService.API/Program.cs

@@ -71,6 +71,9 @@ try
     builder.Services.AddEndpointsApiExplorer();
     builder.Services.AddSwaggerGen();
 
+    // Required by OAuth2Controller to build callback URIs
+    builder.Services.AddHttpContextAccessor();
+
     // Register Serilog.UI with SQLite provider for web log viewer
     builder.Services.AddSerilogUi(options =>
     {