Create a single `currency.ts` utility with `formatPrice`, `formatVND`,
`formatPricePerM2`, and `parseVND` to replace 9+ duplicated inline
formatters. This fixes inconsistent decimal handling (1.5M was truncated
to "1 triệu") and standardises price/m² display. Integrated across
property cards, listing detail, dashboard, analytics, payments, pricing,
and admin moderation pages with 19 new unit tests.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
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