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>

manager_dashboard/src/components/ConfirmModal.jsx

@@ -0,0 +1,14 @@
+export default function ConfirmModal({ title, message, confirmLabel = 'Επιβεβαίωση', confirmClass = 'btn-danger', onConfirm, onCancel }) {
+  return (
+    <div className="fixed inset-0 bg-black/40 flex items-center justify-center z-50 p-4">
+      <div className="bg-white rounded-2xl shadow-xl w-full max-w-sm p-6 space-y-4">
+        <h2 className="text-lg font-bold text-gray-800">{title}</h2>
+        {message && <p className="text-gray-600 text-sm">{message}</p>}
+        <div className="flex gap-3 pt-2">
+          <button onClick={onCancel} className="flex-1 btn btn-secondary">Ακύρωση</button>
+          <button onClick={onConfirm} className={`flex-1 btn ${confirmClass}`}>{confirmLabel}</button>
+        </div>
+      </div>
+    </div>
+  )
+}