Update Makefile

Fixed edge case in serve target by properly handling frontend process cleanup

- Replaced `kill %1` with `kill $$FRONTEND_PID` to ensure correct process termination.
- Captures frontend process PID (`$$!`) explicitly for better reliability.
- Prevents potential issues when multiple background jobs exist.
- Improved Makefile structure for readability and maintainability.

Signed-off-by: Yehowshua <yehowshua@joyofhardware.com>

Makefile

@@ -9,6 +9,7 @@ ELM_MAKE := elm make
 CARGO_BUILD := cargo build
 CARGO_RUN := cargo run
 
+# Ensure exactly one of DEBUG or RELEASE is set
 ifeq ($(DEBUG)$(RELEASE),) # Both are empty
 $(error You must set exactly one of DEBUG=1 or RELEASE=1)
 endif
@@ -20,14 +21,15 @@ endif
 # Targets
 .PHONY: all frontend backend clean serve
 
+# Ensure PUBLIC_DIR exists
 $(PUBLIC_DIR):
 	mkdir -p $(PUBLIC_DIR)
 
+# Copy index.html into PUBLIC_DIR
 $(PUBLIC_DIR)/index.html: $(FRONTEND_DIR)/index.html $(PUBLIC_DIR)
 	cp $< $@
 
-.PHONY: frontend backend
-
+# Frontend build target
 frontend: $(PUBLIC_DIR)/index.html $(PUBLIC_DIR)
 	mkdir -p $(PUBLIC_DIR)/assets
 	make -C $(FRONTEND_DIR)
@@ -35,14 +37,21 @@ frontend: $(PUBLIC_DIR)/index.html $(PUBLIC_DIR)
 	cp $(FRONTEND_DIR)/src/ports.websocket.js $(PUBLIC_DIR)/
 	cp $(FRONTEND_DIR)/assets/CourierPrime-Regular.ttf $(PUBLIC_DIR)/assets/
 
+# Backend build target
 backend:
 	$(CARGO_BUILD) --manifest-path=$(BACKEND_DIR)/Cargo.toml
 
+# Clean target (optional, assuming we want to remove build artifacts)
+clean:
+	rm -rf $(PUBLIC_DIR)
+
+# Serve: Runs both frontend and backend
 serve: frontend backend
 ifeq ($(DEBUG),1)
 	$(MAKE) -C $(FRONTEND_DIR) serve DEBUG=1 & \
+	FRONTEND_PID=$$!; \
 	RUST_LOG=info,actix_web=debug $(CARGO_RUN) --manifest-path=$(BACKEND_DIR)/Cargo.toml; \
-	kill %1
+	kill $$FRONTEND_PID
 else ifeq ($(RELEASE),1)
 	$(CARGO_RUN) --release --manifest-path=$(BACKEND_DIR)/Cargo.toml
 endif