fix(subscriptions): atomic UsageRecord metering to prevent quota bypass

- Add @@unique([subscriptionId, metric, periodStart, periodEnd]) constraint
  to UsageRecord model with corresponding migration
- Replace racy findFirst+update/create pattern with Prisma upsert using
  INSERT ON CONFLICT DO UPDATE SET count = count + delta
- Fix CheckQuotaHandler to use period-scoped findUnique instead of
  unscoped findFirst, preventing stale cross-period reads
- Update tests to reflect atomic upsert pattern

Closes GOO-4

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/app/[locale]/(public)/chuyen-nhuong/page.tsx

@@ -14,15 +14,10 @@ import {
   STATUS_LABELS,
 } from '@/lib/chuyen-nhuong-api';
 import { useTransferListingsSearch } from '@/lib/hooks/use-chuyen-nhuong';
+import { HCM_DISTRICTS } from '@/lib/vietnam-geo';
 
 const PAGE_SIZE = 12;
 
-const DISTRICTS = [
-  'Quận 1', 'Quận 2', 'Quận 3', 'Quận 4', 'Quận 5', 'Quận 6', 'Quận 7',
-  'Quận 8', 'Quận 9', 'Quận 10', 'Quận 11', 'Quận 12', 'Bình Thạnh',
-  'Gò Vấp', 'Phú Nhuận', 'Tân Bình', 'Tân Phú', 'Thủ Đức',
-];
-
 export default function ChuyenNhuongPage() {
   const [filters, setFilters] = React.useState<SearchTransferListingsParams>({
     page: 1,
@@ -93,7 +88,7 @@ export default function ChuyenNhuongPage() {
             aria-label="Quận/Huyện"
           >
             <option value="">Quận/Huyện</option>
-            {DISTRICTS.map((d) => (
+            {HCM_DISTRICTS.map((d) => (
               <option key={d} value={d}>{d}</option>
             ))}
           </select>