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/ProxyPage.tsx

@@ -1,10 +1,11 @@
 import { useEffect, useState, useRef } from 'react';
-import { Form, Input, Switch, Button, Card, message, Row, Col } from 'antd';
+import { Form, Input, Switch, Button, Card, message, Row, Col, theme } from 'antd';
 import { proxyApi } from '../api/modules';
 
 const WS_BASE = `ws://${window.location.hostname}:8000`;
 
 export default function ProxyPage() {
+  const { token } = theme.useToken();
   const [form] = Form.useForm();
   const [loading, setLoading] = useState(false);
   const [testing, setTesting] = useState(false);
@@ -100,10 +101,10 @@ export default function ProxyPage() {
 
 
   const logColors: Record<string, string> = {
-    error: '#ff4d4f',
-    success: '#52c41a',
-    warning: '#faad14',
-    info: '#333',
+    error: token.colorError,
+    success: token.colorSuccess,
+    warning: token.colorWarning,
+    info: token.colorText,
   };
 
   return (
@@ -171,10 +172,10 @@ export default function ProxyPage() {
         styles={{ body: { height: '100%', overflow: 'auto', fontFamily: 'monospace', fontSize: 12, padding: '8px 16px' } }}
       >
         {logs.length === 0 ? (
-          <span style={{ color: '#999' }}>点击"测试代理"或"测试白名单"查看日志</span>
+          <span style={{ color: token.colorTextTertiary }}>点击"测试代理"或"测试白名单"查看日志</span>
         ) : (
           logs.map((log, i) => (
-            <div key={i} style={{ color: logColors[log.level] || '#333', lineHeight: '20px' }}>
+            <div key={i} style={{ color: logColors[log.level] || token.colorText, lineHeight: '20px' }}>
               {log.message}
             </div>
           ))