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/api/src/modules/search/infrastructure/services/search-result-mapper.ts

@@ -27,6 +27,7 @@ export interface RawListingRow {
   viewCount: number;
   saveCount: number;
   projectName: string | null;
+  legalStatus?: string | null;
   amenities: unknown;
   featuredUntil?: Date | string | null;
 }
@@ -60,6 +61,7 @@ export function mapRowToListingDocument(row: RawListingRow): ListingDocument {
     viewCount: row.viewCount ?? 0,
     saveCount: row.saveCount ?? 0,
     projectName: row.projectName,
+    legalStatus: row.legalStatus ?? null,
     amenities: Array.isArray(row.amenities) ? (row.amenities as string[]) : [],
     isFeatured: row.featuredUntil && new Date(row.featuredUntil) > new Date() ? 1 : 0,
   };