feat: 定时执行工单 — 新建工单+自动任务管理全面重构

后端:
- Ticket 模型新增 scheduled_at 字段 (DateTime, nullable)
- TicketStatus 新增 SCHEDULED 状态
- 状态转换图: approved→scheduled, scheduled→executing/approved
- execute_ticket: scheduled_at 在未来时进入 scheduled 状态
- ticket_scheduler.py: asyncio 后台定时执行器
- GET /tickets/scheduled/list: 列出定时执行中工单
- POST /tickets/{id}/cancel-schedule: 取消定时执行

前端:
- TicketCreatePage: 新增定时执行 checkbox + datetime-local picker (秒级精度)
- AutoTaskPage: 全面重写为真实定时任务管理页
  - 实时倒计时显示 (Xh Xm 后执行)
  - DB 类型图标 (MySQL/PG/Redis/MongoDB)
  - SQL 预览 + 取消定时执行
  - 每 30 秒自动刷新

backend/app/api/v1/endpoints/ticket.py

@@ -69,6 +69,7 @@ class TicketStatus(str, Enum):
     PENDING = "pending"       # 待审批
     REVIEWING = "reviewing"   # 审批中（多级审批）
     APPROVED = "approved"     # 已通过
+    SCHEDULED = "scheduled"   # 定时执行中
     REJECTED = "rejected"     # 已拒绝
     EXECUTING = "executing"   # 执行中
     SUCCESS = "success"       # 执行成功
@@ -80,7 +81,8 @@ class TicketStatus(str, Enum):
 TICKET_STATE_TRANSITIONS: Dict[str, List[str]] = {
     TicketStatus.PENDING.value: [TicketStatus.REVIEWING.value, TicketStatus.APPROVED.value, TicketStatus.REJECTED.value],
     TicketStatus.REVIEWING.value: [TicketStatus.REVIEWING.value, TicketStatus.APPROVED.value, TicketStatus.REJECTED.value],
-    TicketStatus.APPROVED.value: [TicketStatus.EXECUTING.value, TicketStatus.REJECTED.value],
+    TicketStatus.APPROVED.value: [TicketStatus.EXECUTING.value, TicketStatus.SCHEDULED.value, TicketStatus.REJECTED.value],
+    TicketStatus.SCHEDULED.value: [TicketStatus.EXECUTING.value, TicketStatus.APPROVED.value],
     TicketStatus.EXECUTING.value: [TicketStatus.SUCCESS.value, TicketStatus.FAILED.value],
     TicketStatus.SUCCESS.value: [TicketStatus.ROLLBACK.value],
     TicketStatus.FAILED.value: [TicketStatus.ROLLBACK.value, TicketStatus.APPROVED.value],
@@ -404,6 +406,7 @@ async def create_ticket(
         applicant_id=current_user.id,
         status=initial_status,
         audit_result=json.dumps(v2_report.to_dict(), ensure_ascii=False) if v2_report and v2_report.findings else None,
+        scheduled_at=data.scheduled_at,
     )
     db.add(ticket)
     await db.flush()  # flush to get ticket.id
@@ -896,7 +899,25 @@ async def execute_ticket(
     # 5. 权限检查
     await check_instance_permission(current_user, instance, "ticket:execute", db)
 
-    # 6. 状态转换: approved -> executing
+    # 6. 定时执行：如果 scheduled_at 在未来，改为 scheduled 状态
+    if ticket.scheduled_at:
+        now = datetime.now(timezone.utc)
+        scheduled_aware = ticket.scheduled_at.replace(tzinfo=timezone.utc) if ticket.scheduled_at.tzinfo is None else ticket.scheduled_at
+        if scheduled_aware > now:
+            if not _validate_status_transition(ticket.status, TicketStatus.SCHEDULED.value):
+                raise HTTPException(status_code=400, detail=f"非法的状态转换: {ticket.status} -> scheduled")
+            ticket.status = TicketStatus.SCHEDULED.value
+            await db.commit()
+            await db.refresh(ticket)
+
+            # 启动后台定时执行
+            from app.services.ticket_scheduler import schedule_ticket_execution
+            await schedule_ticket_execution(ticket.id, scheduled_aware)
+
+            ticket_data = await _enrich_ticket(ticket, db)
+            return ticket_data
+
+    # 7. 状态转换: approved -> executing
     if not _validate_status_transition(ticket.status, TicketStatus.EXECUTING.value):
         raise HTTPException(
             status_code=400,
@@ -907,7 +928,7 @@ async def execute_ticket(
     await db.commit()
     await db.refresh(ticket)
 
-    # 7. 使用多数据库执行引擎
+    # 8. 使用多数据库执行引擎
     from app.services.ticket_executor import TicketExecutor
     executor = TicketExecutor()
 
@@ -1071,3 +1092,69 @@ async def _send_execution_notification(
         channels=channels,
         ticket_data=notification_data,
     )
+
+
+# ===== 定时任务管理 =====
+
+@router.get("/scheduled/list")
+async def list_scheduled_tickets(
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin", "dba")),
+):
+    """列出所有定时执行中的工单。"""
+    result = await db.execute(
+        select(Ticket)
+        .where(Ticket.status == TicketStatus.SCHEDULED.value)
+        .order_by(Ticket.scheduled_at.asc())
+    )
+    tickets = result.scalars().all()
+    data = []
+    for t in tickets:
+        inst_result = await db.execute(select(Instance).where(Instance.id == t.instance_id))
+        inst = inst_result.scalar_one_or_none()
+        data.append({
+            "id": t.id,
+            "ticket_no": t.ticket_no,
+            "title": t.title,
+            "db_type": t.db_type,
+            "instance_name": inst.name if inst else "未知",
+            "instance_db_type": inst.db_type if inst else "",
+            "target_database": t.target_database,
+            "sql_content": t.sql_content[:200] + "..." if len(t.sql_content) > 200 else t.sql_content,
+            "status": t.status,
+            "scheduled_at": t.scheduled_at.isoformat() if t.scheduled_at else None,
+            "priority": t.priority,
+            "create_time": t.create_time.isoformat() if t.create_time else None,
+        })
+    return {"items": data, "total": len(data)}
+
+
+@router.post("/{ticket_id}/cancel-schedule")
+async def cancel_scheduled_ticket(
+    ticket_id: int,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(require_role("admin", "dba")),
+):
+    """取消定时执行，将工单状态改回 approved。"""
+    ticket = await _get_ticket(db, ticket_id)
+    if ticket.status != TicketStatus.SCHEDULED.value:
+        raise HTTPException(status_code=400, detail="只能取消定时执行中的工单")
+
+    if not _validate_status_transition(ticket.status, TicketStatus.APPROVED.value):
+        raise HTTPException(status_code=400, detail="非法的状态转换")
+
+    # 取消后台任务
+    from app.services.ticket_scheduler import cancel_ticket_execution
+    cancel_ticket_execution(ticket.id)
+
+    ticket.status = TicketStatus.APPROVED.value
+    await db.commit()
+    await db.refresh(ticket)
+
+    await AuditLogService.log(
+        db, user_id=current_user.id, action="CANCEL_SCHEDULED_TICKET",
+        target_type="ticket", target_id=ticket.id,
+        detail=f"取消定时执行: {ticket.scheduled_at}",
+    )
+
+    return {"message": "已取消定时执行", "ticket_id": ticket_id, "status": ticket.status}