feat(listings): add user-facing scam/abuse report flow (GOO-19)

- Add ListingFlag model with FlagReason enum (SCAM, DUPLICATE, WRONG_INFO, ALREADY_SOLD, INAPPROPRIATE)
- Add POST /listings/:id/report endpoint with rate limiting and duplicate prevention
- Auto-flag listings with ≥3 reports to PENDING_REVIEW for moderator review
- Add GET /admin/flagged-listings endpoint for admin moderation queue
- Add "Báo cáo" button + modal on listing detail page (Vietnamese UI)
- Add Prisma migration for listing_flags table with unique constraint per user/listing

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

apps/web/components/listings/listing-detail-client.tsx

@@ -9,6 +9,7 @@ import { ImageGallery } from '@/components/listings/image-gallery';
 import { InquiryModal } from '@/components/listings/inquiry-modal';
 import { PriceHistoryChart } from '@/components/listings/price-history-chart';
 import { SocialShare } from '@/components/listings/social-share';
+import { ReportListingModal } from '@/components/listings/report-listing-modal';
 import { Badge } from '@/components/ui/badge';
 import { Button } from '@/components/ui/button';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
@@ -399,6 +400,7 @@ export function ListingDetailClient({ listing }: ListingDetailClientProps) {
   const propertyTypeLabel = getLabel(PROPERTY_TYPES, property.propertyType);
 
   const [inquiryOpen, setInquiryOpen] = React.useState(false);
+  const [reportOpen, setReportOpen] = React.useState(false);
   const [neighborhoodScore, setNeighborhoodScore] = React.useState<NeighborhoodScoreResult | null>(null);
   const [priceHistory, setPriceHistory] = React.useState<PriceHistoryItem[]>([]);
   const [comps, setComps] = React.useState<ListingSimilarItem[]>([]);
@@ -651,7 +653,18 @@ export function ListingDetailClient({ listing }: ListingDetailClientProps) {
                 />
                 <InfoItem label="Hướng" value={getLabel(DIRECTIONS, property.direction) || '---'} />
                 <InfoItem label="Năm xây" value={property.yearBuilt ? `${property.yearBuilt}` : '---'} />
-                <InfoItem label="Pháp lý" value={property.legalStatus || '---'} />
+                <InfoItem label="Pháp lý" value={
+                  (() => {
+                    const labels: Record<string, string> = {
+                      SO_DO: 'Sổ đỏ', SO_HONG: 'Sổ hồng',
+                      LAND_USE_RIGHT: 'Quyền sử dụng đất', JOINT_USE_RIGHT: 'Sở hữu chung',
+                      AWAITING: 'Đang chờ sổ', NO_CERTIFICATE: 'Chưa có giấy tờ',
+                    };
+                    const label = property.legalStatus ? (labels[property.legalStatus] ?? property.legalStatus) : '---';
+                    const badge = property.certificateVerified ? ' ✅ Đã xác minh' : '';
+                    return label + badge;
+                  })()
+                } />
                 <InfoItem label="Dự án" value={property.projectName || '---'} />
                 <InfoItem
                   label="Cách metro gần nhất"
@@ -867,6 +880,24 @@ export function ListingDetailClient({ listing }: ListingDetailClientProps) {
             </CardContent>
           </Card>
 
+          {/* Report */}
+          <Button
+            variant="ghost"
+            size="sm"
+            className="w-full gap-2 text-muted-foreground hover:text-destructive"
+            onClick={() => setReportOpen(true)}
+          >
+            <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M3 21v-4m0 0V5a2 2 0 012-2h6.5l1 1H21l-3 6 3 6h-8.5l-1-1H5a2 2 0 00-2 2zm9-13.5V9" />
+            </svg>
+            Báo cáo tin đăng
+          </Button>
+          <ReportListingModal
+            listingId={listing.id}
+            open={reportOpen}
+            onOpenChange={setReportOpen}
+          />
+
           {/* Stats */}
           <Card>
             <CardContent className="pt-5">