feat: 迭代三大模块 + 全系统 Bug 修复

新功能：
- 账单筛选统计：多维度筛选面板 + 保存方案 + 结果统计
- 通知公告：系统公告/群组通知/个人提醒 + 通知中心页面
- 管理员后台：数据看板 + 用户管理 + 发布公告

Bug 修复：
- 统计页 fetchPrevMonthData/fetchMaxSingle 添加 group_id
- 群组视图添加 t.group_id 过滤，防止私人数据泄露
- 通知列表添加群组通知条件
- 通知标记已读添加错误处理
- 管理员 API 添加 affectedRows 检查
- 筛选面板金额为 0 时正确回填
- profile onShow 补充 userStore.fetchUserInfo
- 全系统样式修复（overflow/box-sizing）

server/src/routes/auth.ts

@@ -23,10 +23,14 @@ router.post('/demo-login', async (_req: Request, res: Response) => {
       [demoOpenid, 'demo', 'demo']
     )
     const userId = (result as any).insertId
+
+    // 首个用户自动设为管理员
+    await autoSetAdmin(userId)
+
     const token = signToken(userId)
-    const [userRows] = await pool.query('SELECT nickname, avatar_url FROM users WHERE id = ?', [userId])
+    const [userRows] = await pool.query('SELECT nickname, avatar_url, role FROM users WHERE id = ?', [userId])
     const userInfo = (userRows as any[])[0]
-    res.json({ code: 0, data: { token, userId, nickname: userInfo?.nickname || '小菜', avatar_url: userInfo?.avatar_url || '' } })
+    res.json({ code: 0, data: { token, userId, nickname: userInfo?.nickname || '小菜', avatar_url: userInfo?.avatar_url || '', role: userInfo?.role || 'user' } })
   } catch (err: any) {
     console.error('[Auth] Demo login failed:', err.message)
     res.status(500).json({ code: 50000, message: '服务器错误' })
@@ -59,15 +63,27 @@ router.post('/login', async (req: Request, res: Response) => {
     )
     const userId = (result as any).insertId
 
+    // 首个用户自动设为管理员
+    await autoSetAdmin(userId)
+
     // HMAC signed token with expiry
     const token = signToken(userId)
-    const [userRows] = await pool.query('SELECT nickname, avatar_url FROM users WHERE id = ?', [userId])
+    const [userRows] = await pool.query('SELECT nickname, avatar_url, role FROM users WHERE id = ?', [userId])
     const userInfo = (userRows as any[])[0]
-    res.json({ code: 0, data: { token, userId, nickname: userInfo?.nickname || '小菜', avatar_url: userInfo?.avatar_url || '' } })
+    res.json({ code: 0, data: { token, userId, nickname: userInfo?.nickname || '小菜', avatar_url: userInfo?.avatar_url || '', role: userInfo?.role || 'user' } })
   } catch (err: any) {
     console.error('[Auth] Login failed:', err.message)
     res.status(500).json({ code: 50000, message: '服务器错误' })
   }
 })
 
+/** 首个用户自动设为管理员 */
+async function autoSetAdmin(userId: number) {
+  const [adminCount] = await pool.query('SELECT COUNT(*) as count FROM users WHERE role = ?', ['admin'])
+  if ((adminCount as any[])[0].count === 0) {
+    await pool.query('UPDATE users SET role = ? WHERE id = ?', ['admin', userId])
+    console.log(`[Auth] User ${userId} auto-promoted to admin`)
+  }
+}
+
 export default router