refactor: migrate API keys to config, extend Kline intervals, add DB extensions

Security:
- Move hardcoded Binance API key/secret from rest.ts to env.yaml (exchange config segment)
- Add ExchangeConfig validation in config/validators.ts
- Export typed exchange config from config/index.ts
- Update AGENTS/07-caveats.md to reflect the new policy

Kline intervals (add 3m / 2h / 6h / 8h / 1mon):
- TypeScript: update KlineInterval type, KLINE_INTERVAL_MS mapping, build_aggregates_sql refresh chain
- Python: sync KlineInterval Literal type, INTERVAL_TO_TABLE and INTERVAL_MS mappings, db_test table list
- SQL: add 5 continuous aggregate materialized views (klines_3m/2h/6h/8h/1mon) with indexes
- SQL: extend default kline_intervals in trading_pairs table
- SQL: add cross-sectional query indexes for klines_1d and klines_1w

DB:
- Enable pg_prewarm extension (backtest warmup)
- Enable pg_stat_statements extension (slow query monitoring)

Other:
- data/run/exchange.ts: graceful pgsql shutdown after backfill completes
- Config path: load from data/env.yaml (symlink) instead of project root

env.yaml

@@ -22,6 +22,12 @@ redis:
   # 是否启用 Pub/Sub 行情发布（开发时可关闭以节省资源）
   publish_enabled: true
 
+# --- 交易所 API 密钥 ---
+exchange:
+  binance:
+    api_key: "ONSJKIGRpDYLn6FdV17aAKfjclZ4I2LzamflhuMpsoRQA427lLKeyJlGtg2RZ7DH"
+    api_secret: "5Mfv4TgvDlRzCHbtl2nJL4mVHUvMm8pyjKiRjMoosBMxrhlqMw6CuQbg2qbS2Npd"
+
 # --- 日志 ---
 logging:
   # 日志级别：trace / debug / info / warn / error / fatal