feat(account): 支持账号级别拦截预热请求

- 新增 intercept_warmup_requests 配置项，存储在 credentials 字段
- 启用后，标题生成、Warmup 等预热请求返回 mock 响应，不消耗上游 token
- 前端支持所有账号类型（OAuth、Setup Token、API Key）的开关配置
- 修复 OAuth 凭证刷新时丢失非 token 配置的问题

frontend/src/i18n/locales/en.ts

@@ -696,6 +696,8 @@ export default {
       enterErrorCode: 'Enter error code (100-599)',
       invalidErrorCode: 'Please enter a valid HTTP error code (100-599)',
       errorCodeExists: 'This error code is already selected',
+      interceptWarmupRequests: 'Intercept Warmup Requests',
+      interceptWarmupRequestsDesc: 'When enabled, warmup requests like title generation will return mock responses without consuming upstream tokens',
       proxy: 'Proxy',
       noProxy: 'No Proxy',
       concurrency: 'Concurrency',