feat: 日志自动清理 — 系统设置+定时任务+手动操作

1. 系统设置新增 cleanup 分组(6项配置):
   - 启用自动清理(开关)
   - 清理执行时间(默认凌晨3点)
   - 工单保留天数(默认90天)
   - 审计日志保留天数(默认180天)
   - 查询历史保留天数(默认30天)
   - 定时任务日志保留天数(默认30天)

2. log_cleanup.py: 自动清理服务
   - 只清理已完成/已拒绝的工单
   - 按保留天数过滤
   - 0天=不清理

3. APScheduler cron job: 每天03:00自动清理

4. API endpoints:
   - POST /settings/cleanup/run — 手动触发清理
   - GET /settings/cleanup/preview — 预览待清理数量

5. 前端 PlatformConfigPage:
   - GROUP_META 新增 cleanup 分组
   - CleanupActions 子组件: 预览+手动清理按钮

6. 清空所有历史工单数据(tickets/ticket_approvals/audit_logs/query_histories)

backend/app/services/settings_seeds.py

@@ -126,6 +126,68 @@ SEED_SETTINGS = [
         "default_value": "true",
         "sort_order": 21,
     },
+
+    # ── 日志清理 ──
+    {
+        "key": "cleanup_enabled",
+        "value": "true",
+        "value_type": "boolean",
+        "group": "cleanup",
+        "label": "启用自动清理",
+        "description": "开启后每天凌晨自动清理过期记录",
+        "default_value": "true",
+        "sort_order": 30,
+    },
+    {
+        "key": "cleanup_run_hour",
+        "value": "3",
+        "value_type": "integer",
+        "group": "cleanup",
+        "label": "清理执行时间（时）",
+        "description": "每天几点执行自动清理（0-23），默认凌晨 3 点",
+        "default_value": "3",
+        "sort_order": 31,
+    },
+    {
+        "key": "cleanup_ticket_days",
+        "value": "90",
+        "value_type": "integer",
+        "group": "cleanup",
+        "label": "数据变更工单保留天数",
+        "description": "已完成/已拒绝的工单超过保留天数将被自动清理（0 表示不清理）",
+        "default_value": "90",
+        "sort_order": 32,
+    },
+    {
+        "key": "cleanup_audit_log_days",
+        "value": "180",
+        "value_type": "integer",
+        "group": "cleanup",
+        "label": "审计日志保留天数",
+        "description": "审计日志超过保留天数将被自动清理（0 表示不清理）",
+        "default_value": "180",
+        "sort_order": 33,
+    },
+    {
+        "key": "cleanup_query_history_days",
+        "value": "30",
+        "value_type": "integer",
+        "group": "cleanup",
+        "label": "查询历史保留天数",
+        "description": "查询历史超过保留天数将被自动清理（0 表示不清理）",
+        "default_value": "30",
+        "sort_order": 34,
+    },
+    {
+        "key": "cleanup_scheduled_task_log_days",
+        "value": "30",
+        "value_type": "integer",
+        "group": "cleanup",
+        "label": "定时任务日志保留天数",
+        "description": "定时任务执行日志超过保留天数将被自动清理（0 表示不清理）",
+        "default_value": "30",
+        "sort_order": 35,
+    },
 ]
 
 # 分组元信息
@@ -133,4 +195,5 @@ SETTING_GROUPS = {
     "query": {"label": "查询控制", "icon": "🔍", "description": "控制查询行为、LIMIT、超时和脱敏策略"},
     "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"},
 }