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)/bao-cao/tao-moi/page.tsx

@@ -9,6 +9,7 @@ import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';
 import { useGenerateReport } from '@/lib/hooks/use-reports';
 import type { ReportType } from '@/lib/reports-api';
+import { HCM_DISTRICTS } from '@/lib/vietnam-geo';
 
 // ─── Constants ─────────────────────────────────────────
 
@@ -18,12 +19,7 @@ const PROVINCES = [
   'Hưng Yên', 'Quảng Ninh', 'Thái Nguyên', 'Vĩnh Phúc', 'Cần Thơ',
 ];
 
-const HCM_DISTRICTS = [
-  'Quận 1', 'Quận 3', 'Quận 4', 'Quận 5', 'Quận 6', 'Quận 7',
-  'Quận 8', 'Quận 10', 'Quận 11', 'Quận 12', 'Bình Thạnh',
-  'Gò Vấp', 'Phú Nhuận', 'Tân Bình', 'Tân Phú', 'Thủ Đức',
-  'Bình Tân', 'Nhà Bè', 'Hóc Môn', 'Củ Chi', 'Cần Giờ',
-];
+const HCM_DISTRICTS_LIST = HCM_DISTRICTS;
 
 const PROPERTY_TYPES = [
   { value: 'APARTMENT', label: 'Căn hộ' },
@@ -248,7 +244,7 @@ export default function TaoMoiPage() {
                     className="mt-1 w-full rounded-md border bg-background px-3 py-2 text-sm"
                   >
                     <option value="">Chọn quận/huyện</option>
-                    {HCM_DISTRICTS.map((d) => (
+                    {HCM_DISTRICTS_LIST.map((d) => (
                       <option key={d} value={d}>{d}</option>
                     ))}
                   </select>
@@ -302,7 +298,7 @@ export default function TaoMoiPage() {
                   className="mt-1 w-full rounded-md border bg-background px-3 py-2 text-sm"
                 >
                   <option value="">Chọn quận/huyện</option>
-                  {HCM_DISTRICTS.map((d) => (
+                  {HCM_DISTRICTS_LIST.map((d) => (
                     <option key={d} value={d}>{d}</option>
                   ))}
                 </select>