feat: 审核规则持久化到DB + 全面配置去硬编码化

- AuditRule模型: 新增code/config_json字段，支持规则编码和阈值参数持久化
- audit_engine_v2: _load_rules从DB读config_json覆盖默认config
- audit_rule_sync: 启动时自动从_RULE_REGISTRY同步规则到DB(239条)
- settings API: update后刷新query_service配置缓存
- query_service: MAX_ROWS/QUERY_TIMEOUT/MAX_QUERY_LENGTH/MAX_RESULT_MEMORY改为动态读取system_settings
- ticket_executor: SQL_TIMEOUT/REDIS_TIMEOUT/MONGO_TIMEOUT改为动态获取
- settings_seeds: 新增executor分组(sql/redis/mongo超时) + query_result_max_memory_mb
- audit_rule endpoint: 移除无效的AuditEngine缓存清理（每次audit是新实例）
- 测试: 1057 passed（修复所有新引入失败，17个历史遗留）

backend/app/main.py

@@ -78,6 +78,26 @@ async def lifespan(app: FastAPI):
     await seed_data()
     await seed_workflows()
 
+    # 同步审核规则到数据库（首次将硬编码 config/severity 写入 DB）
+    try:
+        from app.core.database import async_session
+        async with async_session() as sync_db:
+            from app.services.audit_rule_sync import sync_rules_to_db
+            await sync_rules_to_db(sync_db)
+    except Exception as e:
+        import logging
+        logging.getLogger(__name__).warning("审核规则同步失败: %s", e)
+
+    # 确保所有种子设置项存在（含 executor 分组等新增项）
+    try:
+        from app.core.database import async_session
+        async with async_session() as seed_db:
+            from app.api.v1.endpoints.settings import _ensure_settings
+            await _ensure_settings(seed_db)
+    except Exception as e:
+        import logging
+        logging.getLogger(__name__).warning("种子设置同步失败: %s", e)
+
     # 启动 APScheduler + 恢复定时工单
     from app.services.ticket_scheduler import start_scheduler, recover_scheduled_tickets, shutdown_scheduler
     start_scheduler()