fix: clarify trading status messages

[jackhai9]

Summary

• distinguish zero available balance, zero openable quantity, and unread quantity
• preserve numeric zero during decimal parsing and balance classification
• standardize user-facing trading, cancel, chart, precision, and invariant messages in Chinese
• remove internal implementation details from status feedback

Validation

• npm test (433 passed)
• npm run build:binance-orderbook-trade
• npm run check:binance-orderbook-trade
• npm run inspect:binance-orderbook-trade
• git diff --check