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/services/offlinePayments.js

@@ -0,0 +1,61 @@
+import db from '../db/posdb'
+import client from '../api/client'
+
+/**
+ * Queue an emergency payment locally.
+ * Called in Emergency Mode when the server is unreachable.
+ */
+export async function queueOfflinePayment({ orderId, itemIds, paymentMethod }) {
+  const uuid = crypto.randomUUID()
+  await db.offline_payments.add({
+    uuid,
+    orderId,
+    itemIds,
+    paymentMethod,
+    offlineAt: new Date().toISOString(),
+    synced: 0,
+    isDuplicate: 0,
+  })
+  return uuid
+}
+
+/**
+ * Flush all unsynced offline payments to the server.
+ * Called when the server comes back online.
+ * Returns a summary of { synced, duplicates, failed }.
+ */
+export async function flushOfflinePayments() {
+  // Boolean is not a valid IndexedDB key — load all and filter in JS
+  const all = await db.offline_payments.toArray()
+  const pending = all.filter(p => !p.synced)
+  const results = { synced: 0, duplicates: 0, failed: 0 }
+
+  for (const payment of pending) {
+    try {
+      const res = await client.post(`/api/orders/${payment.orderId}/pay-offline`, {
+        uuid: payment.uuid,
+        item_ids: payment.itemIds,
+        payment_method: payment.paymentMethod,
+        offline_at: payment.offlineAt,
+      })
+      const isDuplicate = res.data.is_duplicate
+      await db.offline_payments.update(payment.localId, {
+        synced: 1,
+        isDuplicate: isDuplicate ? 1 : 0,
+      })
+      isDuplicate ? results.duplicates++ : results.synced++
+    } catch {
+      results.failed++
+    }
+  }
+
+  return results
+}
+
+/**
+ * Count unsynced pending payments (to show badge / warning).
+ */
+export async function pendingPaymentCount() {
+  const all = await db.offline_payments.toArray()
+  return all.filter(p => !p.synced).length
+}