feat: add stop command to Makefile for terminating local servers

Makefile

@@ -1,12 +1,13 @@
 # zhealth Makefile
 # Run `make help` to see available commands
 
-.PHONY: help build release lint typecheck test clean serve
+.PHONY: help build release lint typecheck test clean serve stop
 
 # Default target
 help:
 	@echo "Available commands:"
 	@echo "  make serve     - Start both backend and frontend servers"
+	@echo "  make stop      - Stop running backend and frontend servers"
 	@echo "  make build     - Build for development"
 	@echo "  make release   - Build optimized production bundle"
 	@echo "  make migrate   - Run database migrations"
@@ -16,6 +17,12 @@ help:
 	@echo "  make test      - Run all tests"
 	@echo "  make clean     - Clean build artifacts"
 
+stop:
+	@echo "Stopping backend (port 3000) and frontend (port 5173)..."
+	-@lsof -ti :3000 | xargs -r kill 2>/dev/null || true
+	-@lsof -ti :5173 | xargs -r kill 2>/dev/null || true
+	@echo "Servers stopped"
+
 # Backend commands
 .PHONY: backend-dev backend-build backend-release backend-lint backend-test migrate seed