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

data/db/init-db/02-init-tables.sql

@@ -100,7 +100,7 @@ CREATE TABLE IF NOT EXISTS trading_pairs (
     kline_interval          VARCHAR(100) NOT NULL DEFAULT '1m',
 
     -- K 线合成周期列表（逗号分隔，如 "1m,5m,15m,1h,4h,1d"）
-    kline_intervals         VARCHAR(100) NOT NULL DEFAULT '1m,5m,15m,1h,4h,1d',
+    kline_intervals         VARCHAR(100) NOT NULL DEFAULT '1m,3m,5m,15m,30m,1h,2h,4h,6h,8h,1d,1w,1mon',
 
     -- 历史 K 线最后补全时间（UTC）。默认 Unix epoch 起始，
     -- 新交易对从 epoch 起始时间开始全量补拉。