增加自动亮色/暗色主题切换 + 清理 pyc 文件

- 新建 store/theme.tsx: 亮色/暗色/跟随系统三种模式
- App.tsx: ThemeProvider + ConfigProvider 暗色算法
- MainLayout: 侧边栏主题切换按钮，Sider/Content 随主题变化
- 所有页面硬编码颜色替换为 antd token
- AssignmentsPage: Tag 用预设颜色名适配暗色，未选中背景用 colorBgContainer
- LoginPage: 暗色深色渐变背景
- 从 git 移除所有 __pycache__/*.pyc 文件

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/frontend/src/pages/CookiePage.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState } from 'react';
-import { Table, Button, Card, Row, Col, Statistic, message, Tag, Popconfirm, Space, Typography, Input } from 'antd';
+import { Table, Button, Card, Row, Col, Statistic, message, Tag, Popconfirm, Space, Typography, Input, theme } from 'antd';
 import { DownloadOutlined, DeleteOutlined, CopyOutlined, SearchOutlined } from '@ant-design/icons';
 import { cookieApi } from '../api/modules';
 import { getUser, hasPerm } from '../store/auth';
@@ -8,6 +8,7 @@ import { formatTime } from '../utils/time';
 const { Text } = Typography;
 
 export default function CookiePage() {
+  const { token } = theme.useToken();
   const [cookies, setCookies] = useState<any[]>([]);
   const [loading, setLoading] = useState(false);
   const [selectedRowKeys, setSelectedRowKeys] = useState<React.Key[]>([]);
@@ -184,7 +185,7 @@ export default function CookiePage() {
             <Statistic
               title="已分配"
               value={assignedCount}
-              valueStyle={{ color: '#3f8600' }}
+              valueStyle={{ color: token.colorSuccess }}
             />
           </Card>
         </Col>
@@ -193,7 +194,7 @@ export default function CookiePage() {
             <Statistic
               title="未分配"
               value={unassignedCount}
-              valueStyle={{ color: '#cf1322' }}
+              valueStyle={{ color: token.colorError }}
             />
           </Card>
         </Col>