refactor: migrate wechat to user attributes and enhance users list

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>

frontend/src/api/admin/users.ts

@@ -10,7 +10,7 @@ import type { User, UpdateUserRequest, PaginatedResponse } from '@/types'
  * List all users with pagination
  * @param page - Page number (default: 1)
  * @param pageSize - Items per page (default: 20)
- * @param filters - Optional filters (status, role, search)
+ * @param filters - Optional filters (status, role, search, attributes)
  * @param options - Optional request options (signal)
  * @returns Paginated list of users
  */
@@ -21,17 +21,32 @@ export async function list(
     status?: 'active' | 'disabled'
     role?: 'admin' | 'user'
     search?: string
+    attributes?: Record<number, string>  // attributeId -> value
   },
   options?: {
     signal?: AbortSignal
   }
 ): Promise<PaginatedResponse<User>> {
+  // Build params with attribute filters in attr[id]=value format
+  const params: Record<string, any> = {
+    page,
+    page_size: pageSize,
+    status: filters?.status,
+    role: filters?.role,
+    search: filters?.search
+  }
+
+  // Add attribute filters as attr[id]=value
+  if (filters?.attributes) {
+    for (const [attrId, value] of Object.entries(filters.attributes)) {
+      if (value) {
+        params[`attr[${attrId}]`] = value
+      }
+    }
+  }
+
   const { data } = await apiClient.get<PaginatedResponse<User>>('/admin/users', {
-    params: {
-      page,
-      page_size: pageSize,
-      ...filters
-    },
+    params,
     signal: options?.signal
   })
   return data