feat: 新增任务状态管理和API支持

- 添加任务状态API路由，支持获取当前用户的任务状态和待处理任务列表
- 实现任务追踪服务，使用Redis存储任务状态
- 更新回忆录处理逻辑，集成Celery任务提交和状态更新
- 增强测试用例，支持任务状态的获取和清除功能
- 优化代码结构，提升可读性和维护性

api/routers/tasks.py

@@ -0,0 +1,78 @@
+"""
+任务状态 API 路由
+"""
+from typing import List, Dict
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel
+
+from database.models import User as UserModel
+from middleware.auth import get_current_user
+from services.task_tracker import task_tracker
+
+router = APIRouter(prefix="/api/tasks", tags=["tasks"])
+
+
+class TaskInfo(BaseModel):
+    """任务信息"""
+    task_id: str
+    task_type: str = "memoir"
+    status: str  # pending, running, success, failure
+    created_at: str = None
+    updated_at: str = None
+    result: Dict = None
+
+
+class TasksStatusResponse(BaseModel):
+    """任务状态汇总响应"""
+    total: int
+    pending: int
+    running: int
+    success: int
+    failure: int
+    all_completed: bool
+    tasks: List[TaskInfo]
+
+
+@router.get("/status", response_model=TasksStatusResponse)
+async def get_tasks_status(
+    current_user: UserModel = Depends(get_current_user)
+):
+    """
+    获取当前用户的任务状态汇总
+    
+    用于检查后台任务是否全部完成
+    """
+    status = await task_tracker.check_tasks_status(current_user.id)
+    tasks = await task_tracker.get_user_tasks(current_user.id)
+    
+    return TasksStatusResponse(
+        total=status["total"],
+        pending=status["pending"],
+        running=status["running"],
+        success=status["success"],
+        failure=status["failure"],
+        all_completed=status["all_completed"],
+        tasks=[TaskInfo(**t) for t in tasks]
+    )
+
+
+@router.get("/pending")
+async def get_pending_tasks(
+    current_user: UserModel = Depends(get_current_user)
+):
+    """
+    获取当前用户的待处理任务列表
+    """
+    tasks = await task_tracker.get_pending_tasks(current_user.id)
+    return {"pending_tasks": tasks}
+
+
+@router.delete("/clear")
+async def clear_tasks(
+    current_user: UserModel = Depends(get_current_user)
+):
+    """
+    清除当前用户的所有任务记录
+    """
+    await task_tracker.clear_user_tasks(current_user.id)
+    return {"message": "任务记录已清除"}