feat: implement stock reservation background worker and geocode sync endpoint

backend/internal/server/server.go

@@ -311,6 +311,9 @@ func (s *Server) Start(ctx context.Context) error {
 		ReadHeaderTimeout: 5 * time.Second,
 	}
 
+	// Start Stock Reservation Cleanup Worker
+	s.svc.StartStockCleanupWorker(ctx)
+
 	log.Printf("starting %s on %s", s.cfg.AppName, s.cfg.Addr())
 	return srv.ListenAndServe()
 }

backend/internal/usecase/product_usecase.go

@@ -43,6 +43,24 @@ func (s *Service) ListProducts(ctx context.Context, filter domain.ProductFilter,
 	return &domain.ProductPage{Products: products, Total: total, Page: page, PageSize: pageSize}, nil
 }
 
+// StartStockCleanupWorker runs a background goroutine to expire old reservations.
+func (s *Service) StartStockCleanupWorker(ctx context.Context) {
+	ticker := time.NewTicker(5 * time.Minute)
+	go func() {
+		for {
+			select {
+			case <-ticker.C:
+				if err := s.repo.ExpireReservations(context.Background()); err != nil {
+					fmt.Printf("ERROR: failed to expire stock reservations: %v\n", err)
+				}
+			case <-ctx.Done():
+				ticker.Stop()
+				return
+			}
+		}
+	}()
+}
+
 // ReserveStock creates a temporary hold on inventory.
 func (s *Service) ReserveStock(ctx context.Context, productID, inventoryItemID, buyerID uuid.UUID, quantity int64) (*domain.StockReservation, error) {
 	// 1. Check availability (physical stock - active reservations)