fix(web): consolidate inline currency formatters into shared lib (GOO-205)

Remove 8 inline formatPrice/formatVND/formatPriceM2 functions scattered
across components and pages, replacing them with imports from
@/lib/currency. Add formatVNDFull (full locale, no compact notation) for
chuyen-nhuong pages. Fix price-history-chart off-by-1000 bug caused by
double-dividing through priceToMillions then formatMillions. Add k/m²
branch to formatPricePerM2 for sub-million values.

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

apps/web/components/chuyen-nhuong/transfer-item-table.tsx

@@ -7,14 +7,12 @@ import {
   CONDITION_COLORS,
   CONDITION_LABELS,
 } from '@/lib/chuyen-nhuong-api';
+import { formatVNDFull } from '@/lib/currency';
 
 interface TransferItemTableProps {
   items: TransferItemData[];
 }
 
-function formatVND(value: string): string {
-  return new Intl.NumberFormat('vi-VN').format(Number(value)) + ' \u20ab';
-}
 
 export function TransferItemTable({ items }: TransferItemTableProps) {
   if (items.length === 0) {
@@ -59,12 +57,12 @@ export function TransferItemTable({ items }: TransferItemTableProps) {
               </td>
               <td className="px-3 py-2 text-right">{item.quantity}</td>
               <td className="px-3 py-2 text-right font-medium">
-                {formatVND(item.askingPriceVND)}
+                {formatVNDFull(item.askingPriceVND)}
               </td>
               <td className="px-3 py-2 text-right text-muted-foreground">
                 {item.aiEstimatePriceVND ? (
                   <span title={item.aiConfidence ? `Độ tin cậy: ${Math.round(item.aiConfidence * 100)}%` : undefined}>
-                    {formatVND(item.aiEstimatePriceVND)}
+                    {formatVNDFull(item.aiEstimatePriceVND)}
                   </span>
                 ) : '—'}
               </td>