v0.27.0 — refreshing exchange reserve-wallet labels

Added

• tools/refresh_por.py — refreshes the exchange reserve-wallet labels
  as the exchanges republish their lists: Binance (its PoR feed), HTX (the
  monthly snapshot on its GitHub) and MEXC (the monthly Hacken audit PDF,
  read with a stdlib-only PDF reader; ligatures resolved by checksum). It
  reports newly listed and no-longer-listed wallets; --write adds the new
  ones with the same naming and sources, and marks the others "possibly
  retired" without dropping them. Run for this release:
  • Binance: 3 Bitcoin reserve wallets listed on 2026-10-22 (3,300–5,600 BTC
    each).
  • HTX, snapshot 2026-10-01: its first EVM wallets (3; a contract that holds
    reserves is left out — it is shared, not HTX's), and one Bitcoin wallet
    no longer listed.
  • MEXC: the 2026-10-09 audit reads back the same 41 wallets imported in
    0.26.0 — a cross-check of that import by a second parser.