feat(ui): OpenAI OAuth 账号支持批量 RT 输入创建

新增通过手动输入 Refresh Token 创建 OpenAI OAuth 账号功能，
参考 Anthropic sessionKey 批量创建方式：

- useOpenAIOAuth 添加 validateRefreshToken 方法
- accounts.ts 添加 refreshOpenAIToken API
- AuthInputMethod 类型新增 refresh_token 选项
- 支持多行输入 RT（每行一个）批量创建账号
- 账号名称自动累加后缀 #1, #2 等
- UI 显示 RT 数量徽章和批量创建提示
- 添加中英文 i18n 翻译

frontend/src/i18n/locales/en.ts

@@ -1662,6 +1662,9 @@ export default {
         cookieAuthFailed: 'Cookie authorization failed',
         keyAuthFailed: 'Key {index}: {error}',
         successCreated: 'Successfully created {count} account(s)',
+        batchSuccess: 'Successfully created {count} account(s)',
+        batchPartialSuccess: 'Partial success: {success} succeeded, {failed} failed',
+        batchFailed: 'Batch creation failed',
         // OpenAI specific
         openai: {
           title: 'OpenAI Account Authorization',
@@ -1680,7 +1683,14 @@ export default {
           authCodePlaceholder:
             'Option 1: Copy the complete URL\n(http://localhost:xxx/auth/callback?code=...)\nOption 2: Copy only the code parameter value',
           authCodeHint:
-            'You can copy the entire URL or just the code parameter value, the system will auto-detect'
+            'You can copy the entire URL or just the code parameter value, the system will auto-detect',
+          // Refresh Token auth
+          refreshTokenAuth: 'Manual RT Input',
+          refreshTokenDesc: 'Enter your existing OpenAI Refresh Token(s). Supports batch input (one per line). The system will automatically validate and create accounts.',
+          refreshTokenPlaceholder: 'Paste your OpenAI Refresh Token...\nSupports multiple, one per line',
+          validating: 'Validating...',
+          validateAndCreate: 'Validate & Create Account',
+          pleaseEnterRefreshToken: 'Please enter Refresh Token'
         },
         // Gemini specific
 	        gemini: {