feat: 实现 KPL 系统功能改进计划

1. 课程学习进度追踪
   - 新增 UserCourseProgress 和 UserMaterialProgress 模型
   - 新增 /api/v1/progress/* 进度追踪 API
   - 更新 admin.py 使用真实课程完成率数据

2. 路由权限检查完善
   - 新增前端 permissionChecker.ts 权限检查工具
   - 更新 router/guard.ts 实现团队和课程权限验证
   - 新增后端 permission_service.py

3. AI 陪练音频转文本
   - 新增 speech_recognition.py 语音识别服务
   - 新增 /api/v1/speech/* API
   - 更新 ai-practice-coze.vue 支持语音输入

4. 双人对练报告生成
   - 更新 practice_room_service.py 添加报告生成功能
   - 新增 /rooms/{room_code}/report API
   - 更新 duo-practice-report.vue 调用真实 API

5. 学习提醒推送
   - 新增 notification_service.py 通知服务
   - 新增 scheduler_service.py 定时任务服务
   - 支持钉钉、企微、站内消息推送

6. 智能学习推荐
   - 新增 recommendation_service.py 推荐服务
   - 新增 /api/v1/recommendations/* API
   - 支持错题、能力、进度、热门多维度推荐

7. 安全问题修复
   - DEBUG 默认值改为 False
   - 添加 SECRET_KEY 安全警告
   - 新增 check_security_settings() 检查函数

8. 证书 PDF 生成
   - 更新 certificate_service.py 添加 PDF 生成
   - 添加 weasyprint、Pillow、qrcode 依赖
   - 更新下载 API 支持 PDF 和 PNG 格式

backend/app/services/scheduler_service.py

@@ -0,0 +1,273 @@
+"""
+定时任务服务
+使用 APScheduler 管理定时任务
+"""
+import logging
+from datetime import datetime, timedelta
+from typing import Optional
+from apscheduler.schedulers.asyncio import AsyncIOScheduler
+from apscheduler.triggers.cron import CronTrigger
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
+from sqlalchemy.orm import sessionmaker
+from sqlalchemy import select, and_, func
+
+from app.core.config import settings
+from app.models.user import User
+from app.models.user_course_progress import UserCourseProgress, ProgressStatus
+from app.models.task import Task, TaskAssignment
+
+logger = logging.getLogger(__name__)
+
+# 全局调度器实例
+scheduler: Optional[AsyncIOScheduler] = None
+
+
+async def get_db_session() -> AsyncSession:
+    """获取数据库会话"""
+    engine = create_async_engine(settings.DATABASE_URL, echo=False)
+    async_session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+    return async_session()
+
+
+async def send_learning_reminders():
+    """
+    发送学习提醒
+    
+    检查所有用户的学习进度，对长时间未学习的用户发送提醒
+    """
+    logger.info("开始执行学习提醒任务")
+    
+    try:
+        db = await get_db_session()
+        
+        from app.services.notification_service import NotificationService
+        notification_service = NotificationService(db)
+        
+        # 查找超过3天未学习的用户
+        three_days_ago = datetime.now() - timedelta(days=3)
+        
+        result = await db.execute(
+            select(UserCourseProgress, User).join(
+                User, UserCourseProgress.user_id == User.id
+            ).where(
+                and_(
+                    UserCourseProgress.status == ProgressStatus.IN_PROGRESS.value,
+                    UserCourseProgress.last_accessed_at < three_days_ago,
+                )
+            )
+        )
+        
+        inactive_progress = result.all()
+        
+        for progress, user in inactive_progress:
+            # 获取课程名称
+            from app.models.course import Course
+            course_result = await db.execute(
+                select(Course.name).where(Course.id == progress.course_id)
+            )
+            course_name = course_result.scalar() or "未知课程"
+            
+            days_inactive = (datetime.now() - progress.last_accessed_at).days
+            
+            # 发送提醒
+            await notification_service.send_learning_reminder(
+                user_id=user.id,
+                course_name=course_name,
+                days_inactive=days_inactive,
+            )
+            
+            logger.info(f"已发送学习提醒: user_id={user.id}, course={course_name}")
+        
+        await db.close()
+        logger.info(f"学习提醒任务完成，发送了 {len(inactive_progress)} 条提醒")
+        
+    except Exception as e:
+        logger.error(f"学习提醒任务失败: {str(e)}")
+
+
+async def send_task_deadline_reminders():
+    """
+    发送任务截止提醒
+    
+    检查即将到期的任务，发送提醒给相关用户
+    """
+    logger.info("开始执行任务截止提醒")
+    
+    try:
+        db = await get_db_session()
+        
+        from app.services.notification_service import NotificationService
+        notification_service = NotificationService(db)
+        
+        # 查找3天内到期的未完成任务
+        now = datetime.now()
+        three_days_later = now + timedelta(days=3)
+        
+        result = await db.execute(
+            select(Task, TaskAssignment, User).join(
+                TaskAssignment, Task.id == TaskAssignment.task_id
+            ).join(
+                User, TaskAssignment.user_id == User.id
+            ).where(
+                and_(
+                    Task.end_time.between(now, three_days_later),
+                    TaskAssignment.status.in_(["not_started", "in_progress"]),
+                )
+            )
+        )
+        
+        upcoming_tasks = result.all()
+        
+        for task, assignment, user in upcoming_tasks:
+            await notification_service.send_task_deadline_reminder(
+                user_id=user.id,
+                task_name=task.name,
+                deadline=task.end_time,
+            )
+            
+            logger.info(f"已发送任务截止提醒: user_id={user.id}, task={task.name}")
+        
+        await db.close()
+        logger.info(f"任务截止提醒完成，发送了 {len(upcoming_tasks)} 条提醒")
+        
+    except Exception as e:
+        logger.error(f"任务截止提醒失败: {str(e)}")
+
+
+async def send_weekly_reports():
+    """
+    发送周学习报告
+    
+    每周一发送上周的学习统计报告
+    """
+    logger.info("开始生成周学习报告")
+    
+    try:
+        db = await get_db_session()
+        
+        from app.services.notification_service import NotificationService
+        notification_service = NotificationService(db)
+        
+        # 获取所有活跃用户
+        result = await db.execute(
+            select(User).where(User.is_active == True)
+        )
+        users = result.scalars().all()
+        
+        # 计算上周时间范围
+        today = datetime.now().date()
+        last_week_start = today - timedelta(days=today.weekday() + 7)
+        last_week_end = last_week_start + timedelta(days=6)
+        
+        for user in users:
+            # 统计学习时长
+            study_time_result = await db.execute(
+                select(func.coalesce(func.sum(UserCourseProgress.total_study_time), 0)).where(
+                    and_(
+                        UserCourseProgress.user_id == user.id,
+                        UserCourseProgress.last_accessed_at.between(
+                            datetime.combine(last_week_start, datetime.min.time()),
+                            datetime.combine(last_week_end, datetime.max.time()),
+                        )
+                    )
+                )
+            )
+            study_time = study_time_result.scalar() or 0
+            
+            # 统计完成课程数
+            completed_result = await db.execute(
+                select(func.count(UserCourseProgress.id)).where(
+                    and_(
+                        UserCourseProgress.user_id == user.id,
+                        UserCourseProgress.status == ProgressStatus.COMPLETED.value,
+                        UserCourseProgress.completed_at.between(
+                            datetime.combine(last_week_start, datetime.min.time()),
+                            datetime.combine(last_week_end, datetime.max.time()),
+                        )
+                    )
+                )
+            )
+            courses_completed = completed_result.scalar() or 0
+            
+            # 如果有学习活动，发送报告
+            if study_time > 0 or courses_completed > 0:
+                await notification_service.send_weekly_report(
+                    user_id=user.id,
+                    study_time=study_time,
+                    courses_completed=courses_completed,
+                    exams_passed=0,  # TODO: 统计考试通过数
+                )
+                
+                logger.info(f"已发送周报: user_id={user.id}")
+        
+        await db.close()
+        logger.info("周学习报告发送完成")
+        
+    except Exception as e:
+        logger.error(f"周学习报告发送失败: {str(e)}")
+
+
+def init_scheduler():
+    """初始化定时任务调度器"""
+    global scheduler
+    
+    if scheduler is not None:
+        return scheduler
+    
+    scheduler = AsyncIOScheduler()
+    
+    # 学习提醒：每天上午9点执行
+    scheduler.add_job(
+        send_learning_reminders,
+        CronTrigger(hour=9, minute=0),
+        id="learning_reminders",
+        name="学习提醒",
+        replace_existing=True,
+    )
+    
+    # 任务截止提醒：每天上午10点执行
+    scheduler.add_job(
+        send_task_deadline_reminders,
+        CronTrigger(hour=10, minute=0),
+        id="task_deadline_reminders",
+        name="任务截止提醒",
+        replace_existing=True,
+    )
+    
+    # 周学习报告：每周一上午8点发送
+    scheduler.add_job(
+        send_weekly_reports,
+        CronTrigger(day_of_week="mon", hour=8, minute=0),
+        id="weekly_reports",
+        name="周学习报告",
+        replace_existing=True,
+    )
+    
+    logger.info("定时任务调度器初始化完成")
+    return scheduler
+
+
+def start_scheduler():
+    """启动调度器"""
+    global scheduler
+    
+    if scheduler is None:
+        scheduler = init_scheduler()
+    
+    if not scheduler.running:
+        scheduler.start()
+        logger.info("定时任务调度器已启动")
+
+
+def stop_scheduler():
+    """停止调度器"""
+    global scheduler
+    
+    if scheduler and scheduler.running:
+        scheduler.shutdown()
+        logger.info("定时任务调度器已停止")
+
+
+def get_scheduler() -> Optional[AsyncIOScheduler]:
+    """获取调度器实例"""
+    return scheduler