feat(subdomain): add random second-level mailbox support (#924)

Summary: add random second-level subdomain mailbox creation for web, admin, and
  Telegram.

Scope: worker config, UI toggle, and README/VitePress documentation.

Co-authored-by: wufei <fwu@creams.io>

worker/src/i18n/en.ts

@@ -57,6 +57,7 @@ const messages: LocaleMessages = {
     NameTooShortMsg: "Name is too short",
     NameTooLongMsg: "Name is too long",
     InvalidDomainMsg: "Invalid domain",
+    RandomSubdomainNotAllowedMsg: "Random subdomain is not enabled for this domain",
     AddressAlreadyExistsMsg: "Address already exists",
     MaxAddressCountReachedMsg: "Max address count reached",
     AddressNotBindedMsg: "Address is not binded",

worker/src/i18n/type.ts

@@ -55,6 +55,7 @@ export type LocaleMessages = {
     NameTooShortMsg: string
     NameTooLongMsg: string
     InvalidDomainMsg: string
+    RandomSubdomainNotAllowedMsg: string
     AddressAlreadyExistsMsg: string
     MaxAddressCountReachedMsg: string
     AddressNotBindedMsg: string

worker/src/i18n/zh.ts

@@ -57,6 +57,7 @@ const messages: LocaleMessages = {
     NameTooShortMsg: "名称太短",
     NameTooLongMsg: "名称太长",
     InvalidDomainMsg: "无效的域名",
+    RandomSubdomainNotAllowedMsg: "当前域名未启用随机子域名",
     AddressAlreadyExistsMsg: "邮箱地址已存在",
     MaxAddressCountReachedMsg: "已达到最大地址数量限制",
     AddressNotBindedMsg: "邮箱地址未绑定",