fix: resolve all linting and formatting issues

- Fix error return value checks (errcheck)
- Fix unused parameters by using underscore prefix
- Add missing package comments to all packages
- Fix context key type issue in middleware (use typed contextKey)
- Replace deprecated trace.NewNoopTracerProvider with noop.NewTracerProvider
- Fix embedded field selector in database client
- Remove trailing whitespace
- Remove revive linter (as requested) to avoid stuttering warnings for public API interfaces

All linting and formatting checks now pass.

cmd/platform/main.go

@@ -21,7 +21,7 @@ func main() {
 		fx.Invoke(di.RegisterLifecycleHooks),
 		// Force HTTP server to be created (which triggers all dependencies)
 		// This ensures database, health, metrics, etc. are all created
-		fx.Invoke(func(srv *server.Server, dbClient *database.Client) {
+		fx.Invoke(func(_ *server.Server, _ *database.Client) {
 			// Both server and database are created, hooks are registered
 			// This ensures all providers execute
 		}),