refactor: 移除恢复账号页面的标题和副标题

- 移除「手机号+密码登录」标题
- 移除「输入您的手机号和密码」副标题
- 页面更简洁，顶部只保留「恢复账号」导航标题

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/mobile-app/lib/features/auth/presentation/pages/phone_login_page.dart

@@ -153,24 +153,6 @@ class _PhoneLoginPageState extends ConsumerState<PhoneLoginPage> {
                     child: Column(
               crossAxisAlignment: CrossAxisAlignment.start,
               children: [
-                SizedBox(height: 32.h),
-                // 标题
-                Text(
-                  '手机号+密码登录',
-                  style: TextStyle(
-                    fontSize: 24.sp,
-                    fontWeight: FontWeight.w700,
-                    color: const Color(0xFF5D4037),
-                  ),
-                ),
-                SizedBox(height: 8.h),
-                Text(
-                  '输入您的手机号和密码',
-                  style: TextStyle(
-                    fontSize: 14.sp,
-                    color: const Color(0xFF8B6F47),
-                  ),
-                ),
                 SizedBox(height: 32.h),
                 // 手机号输入框
                 _buildPhoneInput(),