fix: 修复钱包API路径和avatarUrl字段长度问题

- identity-service: avatarUrl字段从VarChar(2000)改为Text类型
- mobile-app: 修复getWalletInfo API路径从/user/$id/wallet改为/user/wallet
- mobile-app: 添加userWallet端点常量

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/services/identity-service/prisma/schema.prisma

@@ -13,7 +13,7 @@ model UserAccount {
   
   phoneNumber     String?  @unique @map("phone_number") @db.VarChar(20)
   nickname        String   @db.VarChar(100)
-  avatarUrl       String?  @map("avatar_url") @db.VarChar(2000)
+  avatarUrl       String?  @map("avatar_url") @db.Text
   
   inviterSequence BigInt?  @map("inviter_sequence")
   referralCode    String   @unique @map("referral_code") @db.VarChar(10)

frontend/mobile-app/lib/core/constants/api_endpoints.dart

@@ -19,6 +19,7 @@ class ApiEndpoints {
   // User (-> Identity Service)
   static const String user = '$apiPrefix/user';
   static const String autoCreate = '$user/auto-create';
+  static const String userWallet = '$user/wallet';  // 获取钱包状态
   static const String profile = '$user/profile';
   static const String updateProfile = '$user/profile/update';
   static const String updateAvatar = '$user/avatar';

frontend/mobile-app/lib/core/services/account_service.dart

@@ -325,14 +325,14 @@ class AccountService {
 
   /// 获取钱包信息 (包含助记词)
   ///
-  /// 用 userSerialNum 查询钱包生成状态和助记词
+  /// 通过 JWT token 获取当前用户的钱包状态
   Future<WalletInfoResponse> getWalletInfo(int userSerialNum) async {
     debugPrint('$_tag getWalletInfo() - 开始获取钱包信息');
     debugPrint('$_tag getWalletInfo() - userSerialNum: $userSerialNum');
 
     try {
-      debugPrint('$_tag getWalletInfo() - 调用 GET /user/$userSerialNum/wallet');
-      final response = await _apiClient.get('/user/$userSerialNum/wallet');
+      debugPrint('$_tag getWalletInfo() - 调用 GET /user/wallet');
+      final response = await _apiClient.get('/user/wallet');
       debugPrint('$_tag getWalletInfo() - API 响应状态码: ${response.statusCode}');
 
       if (response.data == null) {