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/data/service.py

@@ -32,6 +32,7 @@ from ..common.models import Kline, KlineInterval
 # ── 周期 → 表名映射 ──
 INTERVAL_TO_TABLE: dict[KlineInterval, str] = {
     "1m": "klines",
+    "3m": "klines_3m",
     "5m": "klines_5m",
     "15m": "klines_15m",
     "30m": "klines_30m",
@@ -39,13 +40,16 @@ INTERVAL_TO_TABLE: dict[KlineInterval, str] = {
     "2h": "klines_2h",
     "4h": "klines_4h",
     "6h": "klines_6h",
+    "8h": "klines_8h",
     "1d": "klines_1d",
     "1w": "klines_1w",
+    "1mon": "klines_1mon",
 }
 
 # ── 周期毫秒数 ──
 INTERVAL_MS: dict[KlineInterval, int] = {
     "1m": 60_000,
+    "3m": 180_000,
     "5m": 300_000,
     "15m": 900_000,
     "30m": 1_800_000,
@@ -53,8 +57,10 @@ INTERVAL_MS: dict[KlineInterval, int] = {
     "2h": 7_200_000,
     "4h": 14_400_000,
     "6h": 21_600_000,
+    "8h": 28_800_000,
     "1d": 86_400_000,
     "1w": 604_800_000,
+    "1mon": 2_592_000_000,
 }
 
 DEFAULT_BATCH_SIZE = 5000