fix(6): fix TypeScript type consistency issues

- Make Item.id required (items from DB always have id)
- Use shared Item type from db.ts in QuantityAdjustmentModal
- Show full npm build output instead of silencing errors
- Ensures all modals use consistent type definitions

start_servers.py

@@ -112,12 +112,13 @@ class StandaloneServerManager:
         # Build if needed
         if not (frontend_dir / ".next" / "standalone").exists():
             self.log("Building Next.js application...")
-            subprocess.run(
+            result = subprocess.run(
                 ["npm", "run", "build"],
                 cwd=str(frontend_dir),
-                check=True,
-                capture_output=True
+                capture_output=False
             )
+            if result.returncode != 0:
+                self.error(f"Frontend build failed with exit code {result.returncode}")
 
     def start_backend(self):
         """Start FastAPI backend server using uvicorn from project root"""