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

frontend/components/inventory/QuantityAdjustmentModal.tsx

@@ -4,16 +4,7 @@ import { useState, useEffect } from 'react';
 import { X } from 'lucide-react';
 import QuantityDisplay from './QuantityDisplay';
 import axios from 'axios';
-
-interface Item {
-  id: number;
-  name: string;
-  quantity: number;
-  part_number?: string;
-  barcode?: string;
-  category?: string;
-  description?: string;
-}
+import { Item } from '@/lib/db';
 
 interface QuantityAdjustmentModalProps {
   item: Item | null;

frontend/lib/db.ts

@@ -1,7 +1,7 @@
 import Dexie, { Table } from 'dexie';
 
 export interface Item {
-  id?: number;
+  id: number;
   barcode: string;
   name: string;
   category: string;

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"""