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

engine/db_test.py

@@ -16,13 +16,18 @@ from common.config import config as app_config
 # ── 各周期对应的表/视图 ──
 INTERVAL_TABLES: dict[str, str] = {
     "1m": "klines",
+    "3m": "klines_3m",
     "5m": "klines_5m",
     "15m": "klines_15m",
     "30m": "klines_30m",
     "1h": "klines_1h",
+    "2h": "klines_2h",
     "4h": "klines_4h",
+    "6h": "klines_6h",
+    "8h": "klines_8h",
     "1d": "klines_1d",
     "1w": "klines_1w",
+    "1mon": "klines_1mon",
 }
 
 LIMIT = 5