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/services/settings_seeds.py

@@ -188,6 +188,48 @@ SEED_SETTINGS = [
         "default_value": "30",
         "sort_order": 35,
     },
+
+    # ── 执行器 ──
+    {
+        "key": "executor_sql_timeout",
+        "value": "60",
+        "value_type": "integer",
+        "group": "executor",
+        "label": "SQL 执行超时（秒）",
+        "description": "MySQL/PostgreSQL 工单执行单条 SQL 最大时间。范围: 10~600",
+        "default_value": "60",
+        "sort_order": 40,
+    },
+    {
+        "key": "executor_redis_timeout",
+        "value": "30",
+        "value_type": "integer",
+        "group": "executor",
+        "label": "Redis 执行超时（秒）",
+        "description": "Redis 工单执行单条命令最大时间。范围: 5~120",
+        "default_value": "30",
+        "sort_order": 41,
+    },
+    {
+        "key": "executor_mongo_timeout",
+        "value": "60",
+        "value_type": "integer",
+        "group": "executor",
+        "label": "MongoDB 执行超时（秒）",
+        "description": "MongoDB 工单执行单条命令最大时间。范围: 10~600",
+        "default_value": "60",
+        "sort_order": 42,
+    },
+    {
+        "key": "query_result_max_memory_mb",
+        "value": "50",
+        "value_type": "integer",
+        "group": "query",
+        "label": "查询结果内存上限（MB）",
+        "description": "单次查询结果集最大内存占用，超限自动截断。范围: 10~500",
+        "default_value": "50",
+        "sort_order": 8,
+    },
 ]
 
 # 分组元信息
@@ -196,4 +238,5 @@ SETTING_GROUPS = {
     "security": {"label": "安全设置", "icon": "🔒", "description": "登录安全、密码策略、审计日志"},
     "ticket": {"label": "工单设置", "icon": "📋", "description": "审批流程、回滚策略"},
     "cleanup": {"label": "日志清理", "icon": "🧹", "description": "数据变更工单、审计日志、查询历史的自动清理策略"},
+    "executor": {"label": "执行器", "icon": "⚙️", "description": "SQL/Redis 执行超时、批量限制、连接参数"},
 }