feat: initial commit — local services (backend + manager dashboard + waiter PWA)

Includes all work to date:
- local_backend: FastAPI backend with products, orders, tables, shifts, cloud sync
- manager_dashboard: React manager UI with product/category management, reports, settings
- waiter_pwa: React PWA for waiter devices
- Category reparent endpoint and UI
- Waiter domain: local_ip sent on heartbeat, waiter_domain persisted from cloud response
- QR code modal in AppInfoTab for waiter domain
- Product form: number input spinners removed, category pre-selected on new product
- Category row: count badge moved to far right

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

waiter_pwa/src/components/ConnectionBanner.jsx

@@ -0,0 +1,14 @@
+export default function ConnectionBanner() {
+  return (
+    <div style={{
+      background: '#7f1d1d',
+      color: '#fca5a5',
+      textAlign: 'center',
+      padding: '8px 16px',
+      fontSize: 13,
+      fontWeight: 600,
+    }}>
+      ⚠ Cannot reach the system — check your WiFi
+    </div>
+  )
+}