feat: 系统配置 + 用户签名

- 新增 sys_config 表，存储应用版本号、标语、描述
- 关于小菜弹窗版本号改为从数据库动态获取
- 用户表新增 slogan 字段（个性签名）
- 编辑资料页面支持修改签名
- 管理后台新增系统配置管理页面
- 更新 CLAUDE.md 文档

server/src/routes/user.ts

@@ -48,7 +48,7 @@ const upload = multer({
 router.get('/me', async (req: AuthRequest, res: Response) => {
   try {
     const [rows] = await pool.query(
-      'SELECT id, nickname, avatar_url, role, created_at FROM users WHERE id = ?',
+      'SELECT id, nickname, avatar_url, slogan, role, created_at FROM users WHERE id = ?',
       [req.userId]
     )
     const user = (rows as any[])[0]
@@ -62,10 +62,10 @@ router.get('/me', async (req: AuthRequest, res: Response) => {
   }
 })
 
-/** 更新用户昵称 */
+/** 更新用户昵称/签名 */
 router.put('/me', async (req: AuthRequest, res: Response) => {
   try {
-    const { nickname } = req.body
+    const { nickname, slogan } = req.body
 
     if (nickname !== undefined) {
       if (typeof nickname !== 'string' || nickname.trim().length === 0) {
@@ -76,6 +76,15 @@ router.put('/me', async (req: AuthRequest, res: Response) => {
       }
     }
 
+    if (slogan !== undefined) {
+      if (typeof slogan !== 'string') {
+        return res.status(400).json({ code: 40001, message: '签名格式错误' })
+      }
+      if (slogan.length > 100) {
+        return res.status(400).json({ code: 40001, message: '签名不能超过100个字符' })
+      }
+    }
+
     const updates: string[] = []
     const params: any[] = []
 
@@ -84,6 +93,11 @@ router.put('/me', async (req: AuthRequest, res: Response) => {
       params.push(nickname.trim())
     }
 
+    if (slogan !== undefined) {
+      updates.push('slogan = ?')
+      params.push(slogan.trim())
+    }
+
     if (updates.length === 0) {
       return res.status(400).json({ code: 40001, message: '没有需要更新的字段' })
     }