feat: 添加工作任务管理功能

- 新增 Task 模型（状态、优先级、进展百分比）
- 任务 API（列表、统计、进展更新、完成标记）
- 前端任务板块（统计卡片 + 任务列表）
- 进展可视化（进度条 + 进展记录）

backend/diary/views.py

@@ -2,8 +2,8 @@ from rest_framework import viewsets
 from rest_framework.decorators import action
 from rest_framework.response import Response
 from django.utils import timezone
-from .models import DiaryEntry, DailyProgress, Experience
-from .serializers import DiaryEntrySerializer, DailyProgressSerializer, ExperienceSerializer
+from .models import DiaryEntry, DailyProgress, Experience, Task
+from .serializers import DiaryEntrySerializer, DailyProgressSerializer, ExperienceSerializer, TaskSerializer
 
 class DiaryEntryViewSet(viewsets.ModelViewSet):
     queryset = DiaryEntry.objects.all()
@@ -60,3 +60,59 @@ class ExperienceViewSet(viewsets.ModelViewSet):
         experiences = Experience.objects.order_by('-date', '-created_at')[:10]
         serializer = self.get_serializer(experiences, many=True)
         return Response(serializer.data)
+
+
+class TaskViewSet(viewsets.ModelViewSet):
+    queryset = Task.objects.all()
+    serializer_class = TaskSerializer
+
+    @action(detail=False, methods=['get'])
+    def by_status(self, request):
+        """按状态分组获取任务"""
+        statuses = {}
+        for task in Task.objects.all():
+            status = task.get_status_display()
+            if status not in statuses:
+                statuses[status] = []
+            statuses[status].append(TaskSerializer(task).data)
+        return Response(statuses)
+
+    @action(detail=False, methods=['get'])
+    def active(self, request):
+        """获取活跃任务（未完成和未取消）"""
+        tasks = Task.objects.exclude(status__in=['completed', 'cancelled'])
+        serializer = self.get_serializer(tasks, many=True)
+        return Response(serializer.data)
+
+    @action(detail=False, methods=['get'])
+    def stats(self, request):
+        """获取任务统计"""
+        total = Task.objects.count()
+        completed = Task.objects.filter(status='completed').count()
+        in_progress = Task.objects.filter(status='in_progress').count()
+        pending = Task.objects.filter(status='pending').count()
+        blocked = Task.objects.filter(status='blocked').count()
+        return Response({
+            'total': total,
+            'completed': completed,
+            'in_progress': in_progress,
+            'pending': pending,
+            'blocked': blocked,
+            'completion_rate': round(completed / total * 100, 1) if total > 0 else 0
+        })
+
+    @action(detail=True, methods=['post'])
+    def update_progress(self, request, pk=None):
+        """更新任务进展"""
+        task = self.get_object()
+        percent = request.data.get('percent', task.progress_percent)
+        notes = request.data.get('notes', '')
+        task.update_progress(int(percent), notes)
+        return Response(TaskSerializer(task).data)
+
+    @action(detail=True, methods=['post'])
+    def complete(self, request, pk=None):
+        """标记任务为完成"""
+        task = self.get_object()
+        task.mark_completed()
+        return Response(TaskSerializer(task).data)