The TCBS `apipubaws.tcbs.com.vn` host returns HTTP 404/500 for every
request, so every ticker resolved as "Unknown stock ticker" and /trade_buy
was unusable. Switch price + symbol resolution to the KBS public endpoint
that vnstock currently defaults to (`kbbuddywts.kbsec.com.vn/iis-server/
investment/stocks/{TICKER}/data_day`). KBS needs no auth, returns JSON,
and is Worker-compatible.
- `prices.fetchStockPrice` now queries KBS with a 14-day lookback window
(covers weekends/holidays) and drops the TCBS-specific ×1000 scaling;
KBS returns real VND.
- `symbols.resolveSymbol` delegates to `fetchStockPrice` for existence
checks — empty `data_day` means unknown ticker.
- Update test fetch stubs to match the `kbsec` host and KBS response
shape (`{ symbol, data_day: [{ c }] }`).
- trading_trades table (migration 0001) persists every buy/sell via optional onTrade callback
- /history [n] command shows caller's last N trades (default 10, max 50), HTML-escaped
- daily cron at 0 17 * * * trims to 1000/user + 10000/global via FIFO delete
- persistence failure logs but does not fail the trade reply
tiennm99