fix: 管理员重置配额补全 monthly 字段并修复 ristretto 缓存异步问题

- 后端 handler：ResetSubscriptionQuotaRequest 新增 Monthly 字段，
  验证逻辑扩展为 daily/weekly/monthly 至少一项为 true
- 后端 service：AdminResetQuota 新增 resetMonthly 参数，
  调用 ResetMonthlyUsage；重置后追加 subCacheL1.Wait()，
  保证 ristretto Del() 的异步删除立即生效，消除重置后
  /v1/usage 返回旧用量数据的竞态窗口
- 后端测试：更新存量测试用例匹配新签名，补充
  TestAdminResetQuota_ResetMonthlyOnly /
  TestAdminResetQuota_ResetMonthlyUsageError 两个新用例
- 前端 API：resetQuota options 类型新增 monthly: boolean
- 前端视图：confirmResetQuota 改为同时重置 daily/weekly/monthly
- i18n：中英文确认提示文案更新，提及每月配额

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/admin/subscriptions.ts

@@ -121,14 +121,14 @@ export async function revoke(id: number): Promise<{ message: string }> {
 }
 
 /**
- * Reset daily and/or weekly usage quota for a subscription
+ * Reset daily, weekly, and/or monthly usage quota for a subscription
  * @param id - Subscription ID
  * @param options - Which windows to reset
  * @returns Updated subscription
  */
 export async function resetQuota(
   id: number,
-  options: { daily: boolean; weekly: boolean }
+  options: { daily: boolean; weekly: boolean; monthly: boolean }
 ): Promise<UserSubscription> {
   const { data } = await apiClient.post<UserSubscription>(
     `/admin/subscriptions/${id}/reset-quota`,