- market/api_client.go: check StatusCode for exchangeInfo, klines, price
endpoints + add truncateBody helper for safe error messages
- market/data.go: check StatusCode for openInterest and premiumIndex
- provider/coinank: check StatusCode for GET and POST requests
- provider/twelvedata: check StatusCode for time series and quote APIs
- Prevents confusing JSON unmarshal errors when APIs return 429/500/etc
- implement coinank free kline api in coinank_api.Kline
- implement coinank free kline ws in coinank_api.KlineWs. if needKline is true, kline data read from KlineCh. if needTicker is true, tickers data read from TickersCh.