Phase4剩余: 推广+成就系统前后端完成 (promotion + achievement)

- 新增: Achievement.tsx 成就系统前端页面 (644行)
- 新增: achievement_admin.py 成就系统后端API (9个端点)
- 新增: migration SQL (achievements, user_achievements, achievement_progress_log)
- 更新: api/index.ts 添加推广+成就API方法 (23个方法)
- 更新: App.tsx 添加 /admin/promotion 和 /admin/achievement 路由
- 更新: AdminLayout.tsx 添加成就系统导航项和图标
- 修复: Promotion.tsx 导入路径 (@/utils/api → @/api)
- 前端构建: 472 modules, 11.23s, 成功
- API测试: 全部6个端点返回 code=0

frontend/src/App.tsx

@@ -40,6 +40,8 @@ import AdminCodeExec from '@/pages/admin/CodeExec';;
 import DistributionBuilder from '@/pages/admin/DistributionBuilder';
 import PrivacySettings from '@/pages/admin/PrivacySettings';
 import ImBots from '@/pages/admin/ImBots';
+import Promotion from '@/pages/admin/Promotion';
+import Achievement from '@/pages/admin/Achievement';
 
 const App: React.FC = () => {
   const [user, setUser] = useState<User | null>(null);
@@ -123,6 +125,8 @@ const App: React.FC = () => {
           <Route path="distributions" element={<DistributionBuilder />} />
           <Route path="im-bots" element={<ImBots />} />
           <Route path="privacy" element={<PrivacySettings />} />
+          <Route path="promotion" element={<Promotion />} />
+          <Route path="achievement" element={<Achievement />} />
         </Route>
 
         <Route path="*" element={<Navigate to="/" />} />