fix: improve HTTP server startup with better error detection

- Added better error detection for HTTP server startup
- Added connectivity check to verify server is actually listening
- Increased wait time to 500ms for better error detection
- Added warning log if server connectivity check fails (may still be starting)
- Improved logging messages for server startup

This should help diagnose why the HTTP server isn't starting and provide better visibility into the startup process.

internal/di/providers.go

@@ -145,7 +145,7 @@ func ProvideErrorBus() fx.Option {
 func ProvideHealthRegistry() fx.Option {
 	return fx.Provide(func(dbClient *database.Client) (*health.Registry, error) {
 		registry := health.NewRegistry()
-		
+
 		// Register database health checker
 		registry.Register("database", health.NewDatabaseChecker(dbClient))
 
@@ -237,19 +237,54 @@ func ProvideHTTPServer() fx.Option {
 					host = "0.0.0.0"
 				}
 				addr := fmt.Sprintf("%s:%d", host, port)
-				
+
+				log.Info("HTTP server starting",
+					logger.String("addr", addr),
+				)
+
 				// Start server in a goroutine
+				// ListenAndServe blocks, so we need to start it async
+				// If there's an immediate error (like port in use), it will return quickly
+				errChan := make(chan error, 1)
 				go func() {
-					log.Info("HTTP server starting",
-						logger.String("addr", addr),
-					)
 					if err := srv.Start(); err != nil && err != http.ErrServerClosed {
-						log.Error("HTTP server error",
+						log.Error("HTTP server failed",
 							logger.String("error", err.Error()),
 						)
+						select {
+						case errChan <- err:
+						default:
+						}
 					}
 				}()
-				return nil
+
+				// Wait a short time to detect immediate binding errors
+				// If ListenAndServe fails immediately (e.g., port in use), it will return quickly
+				select {
+				case err := <-errChan:
+					return fmt.Errorf("HTTP server failed to start: %w", err)
+				case <-time.After(500 * time.Millisecond):
+					// If no error after 500ms, verify server is actually listening
+					// by attempting a connection
+					client := &http.Client{Timeout: 1 * time.Second}
+					checkURL := fmt.Sprintf("http://localhost:%d/healthz", port)
+					resp, err := client.Get(checkURL)
+					if err != nil {
+						// Server might still be starting, but log the attempt
+						log.Warn("Could not verify HTTP server is listening (may still be starting)",
+							logger.String("url", checkURL),
+							logger.String("error", err.Error()),
+						)
+						// Continue anyway - server might still be starting
+					} else {
+						resp.Body.Close()
+					}
+					
+					log.Info("HTTP server started successfully",
+						logger.String("addr", addr),
+					)
+					return nil
+				}
 			},
 			OnStop: func(ctx context.Context) error {
 				return srv.Shutdown(ctx)