GitLab

Migrate the hardcoded wechat field to the new extensible user
attributes system and improve the users management UI.

Migration:
- Add migration 019 to move wechat data to user_attribute_values
- Remove wechat field from User entity, DTOs, and API contracts
- Clean up wechat-related code from backend and frontend

UsersView enhancements:
- Add text labels to action buttons (Filter Settings, Column Settings,
  Attributes Config) for better UX
- Change status column to show colored dot + Chinese text instead of
  English text
- Add dynamic attribute columns support with batch loading
- Add column visibility settings with localStorage persistence
- Add filter settings modal for search and filter preferences
- Update i18n translations

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

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

修复 PR #36 合并后部分 admin handler 直接返回 service 层对象导致
JSON 字段名为 PascalCase 而非期望的 snake_case 问题。

修复内容:
- account_handler: Refresh 接口添加 dto.AccountFromService
- openai_oauth_handler: RefreshAccountToken/CreateAccountFromOAuth 添加 dto 转换
- subscription_handler: BulkAssign 添加 dto.BulkAssignResultFromService
- usage_handler: List 接口添加 dto.UsageLogFromService 转换
- 新增 dto.BulkAssignResult 类型和对应的 mapper 函数