refactor(web): dedup tỷ/triệu compact formatters (GOO-206)

- Add `formatCompact` as an exported alias for `formatPrice` in lib/currency.ts
- Replace 5 inline copies of the tỷ/triệu compact formatter:
  - components/map/listing-map.tsx (local `formatPrice` fn)
  - components/agents/agent-profile-client.tsx (local `fmtVND` fn)
  - app/(dashboard)/dashboard/saved-searches/page.tsx (local `formatPrice` fn)
  - app/(public)/page.tsx (local `formatVnd` fn + `vndFmt` Intl instance)
  - components/listings/price-history-chart.tsx (local `formatMillions` + `priceToMillions`)

All call sites now import from the canonical lib/currency module.
PriceHistoryChart now stores raw VND in chart data (was: millions) so
formatCompact emits correct tỷ/triệu labels using canonical thresholds.

Pre-existing test failures in inquiry/lead/AVM specs are unrelated to this change.

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

apps/web/components/agents/agent-profile-client.tsx

@@ -39,6 +39,7 @@ import { Button } from '@/components/ui/button';
 import { Card, CardContent, CardHeader, CardTitle, CardDescription } from '@/components/ui/card';
 import { Link } from '@/i18n/navigation';
 import type { AgentPublicProfile, AgentReviewItem } from '@/lib/agents-api';
+import { formatCompact } from '@/lib/currency';
 import { shimmerBlurDataURL } from '@/lib/image-blur';
 import type { ListingDetail } from '@/lib/listings-api';
 
@@ -48,12 +49,6 @@ import type { ListingDetail } from '@/lib/listings-api';
 
 const VND = new Intl.NumberFormat('vi-VN');
 
-function fmtVND(value: string | number | bigint): string {
-  const n = typeof value === 'bigint' ? Number(value) : Number(value);
-  if (n >= 1_000_000_000) return `${(n / 1_000_000_000).toFixed(1)} tỷ`;
-  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(0)} tr`;
-  return VND.format(n);
-}
 
 function qualityLabel(score: number): string {
   if (score >= 80) return 'Xuất sắc';
@@ -145,7 +140,7 @@ const listingColumns: DataTableColumn<ListingDetail>[] = [
     sortValue: (row) => Number(row.priceVND),
     cell: (row) => (
       <span className="text-xs font-semibold tabular-nums text-primary">
-        {fmtVND(row.priceVND)}
+        {formatCompact(row.priceVND)}
       </span>
     ),
     width: '12%',
@@ -160,7 +155,7 @@ const listingColumns: DataTableColumn<ListingDetail>[] = [
     cell: (row) =>
       row.pricePerM2 != null ? (
         <span className="text-xs tabular-nums text-foreground-muted">
-          {fmtVND(row.pricePerM2)}
+          {formatCompact(row.pricePerM2)}
         </span>
       ) : (
         <span className="text-xs text-foreground-dim">—</span>
@@ -384,7 +379,7 @@ export function AgentProfileClient({
         />
         <KpiCard
           label="Giá TB"
-          value={avgPriceVND != null ? fmtVND(avgPriceVND) : '—'}
+          value={avgPriceVND != null ? formatCompact(avgPriceVND) : '—'}
           icon={<BarChart2 className="h-4 w-4" />}
           footnote="Danh mục hiện tại"
         />