feat: Bot API L1-L4风险分级标注 + 操作审计日志

- 新增 app/risk_levels.py: RISK_LEVELS定义 + @risk_level装饰器 + API_RISK_MAP
  (L1只读21 / L2业务写5 / L3批量写3 / L4=0安全底线)
- 新增 app/api/audit_log.py: Bot API审计中间件 → backend/logs/bot_audit.log
  (JSON行: timestamp/bot_name/endpoint/method/risk_level/entity_id/status,
   L3额外记rows行数, 不阻塞业务)
- bot_bridge/bot_bridge_v2/bot_kpis/bot_iron_law 全部29路由标注级别
- 新增 GET /api/cma/bot/risk-levels (X-BOT-KEY鉴权): API→级别→处理方式清单
- main.py 注册审计中间件
- tests/test_risk_levels.py: 覆盖路由标注/risk-levels端点/L4不存在/审计日志

backend/app/api/bot_iron_law.py

@@ -9,6 +9,7 @@ from sqlalchemy.orm import Session
 from sqlalchemy import func
 from app.database import get_db
 from app.models import ActionPlan
+from app.risk_levels import risk_level
 
 logger = logging.getLogger("cma.iron_law")
 
@@ -150,6 +151,7 @@ def _query_action_plan_verify(db: Session):
 # ═══════════════ 端点 ═══════════════
 
 @router.get("/iron-law")
+@risk_level("L1")
 def get_iron_law_kpis(
     bot: dict = Depends(verify_bot_key),
     db: Session = Depends(get_db),
@@ -224,6 +226,7 @@ def get_iron_law_kpis(
 
 
 @router.get("/iron-law/bots")
+@risk_level("L1")
 def get_bot_iron_law_ranking(
     bot: dict = Depends(verify_bot_key),
     db: Session = Depends(get_db),