feat: 实现设置账号并发数功能（支持 bulk-update 与 fallback 逐个更新）

frontend/src/api/index.ts

@@ -343,6 +343,15 @@ export interface CleanupInvalidAccountsItem {
   message: string
 }
 
+export interface SetConcurrencyItem {
+  account_id: string
+  account_name: string | null
+  old_concurrency: number | null
+  target_concurrency: number
+  status: string
+  message: string
+}
+
 export const websitesApi = {
   list: () => api.get<WebsiteData[]>('/api/websites'),
   create: (data: WebsiteForm) => api.post<WebsiteData>('/api/websites', data),
@@ -374,6 +383,8 @@ export const websitesApi = {
     api.post<{ success: boolean; message: string; items: CleanupInvalidAccountsItem[] }>(`/api/websites/${id}/accounts/cleanup-invalid/preview`),
   cleanupExecute: (id: number) =>
     api.post<{ success: boolean; message: string; items: CleanupInvalidAccountsItem[] }>(`/api/websites/${id}/accounts/cleanup-invalid/execute`),
+  setConcurrency: (id: number, data: { concurrency: number }) =>
+    api.post<{ success: boolean; message: string; items: SetConcurrencyItem[] }>(`/api/websites/${id}/accounts/set-concurrency`, data),
   listBindings: () => api.get<GroupBindingData[]>('/api/group-bindings'),
   createBinding: (data: GroupBindingForm) => api.post<GroupBindingData>('/api/group-bindings', data),
   updateBinding: (id: number, data: Partial<GroupBindingForm>) => api.put<GroupBindingData>(`/api/group-bindings/${id}`, data),