feat: add Telegram account linking UI with CSRF protection

- TelegramLinkWidget component with Login Widget for browser users
- One-click initData linking for Mini App users
- LinkTelegramCallback page with CSRF state validation
- URL credential clearing via history.replaceState
- Merge flow support with replace navigation
- i18n keys for all 4 locales (ru, en, zh, fa)

src/locales/en.json

@@ -3615,6 +3615,8 @@
       "unlinkError": "Failed to disconnect account",
       "goToAccounts": "Connected Accounts",
       "linking": "Linking account...",
+      "linkTelegramWidget": "Sign in with Telegram to connect",
+      "linkingTelegram": "Connecting Telegram...",
       "providers": {
         "telegram": "Telegram",
         "email": "Email",

src/locales/fa.json

@@ -3051,6 +3051,8 @@
       "unlinkError": "قطع اتصال ناموفق بود",
       "goToAccounts": "حساب‌های متصل",
       "linking": "در حال اتصال حساب...",
+      "linkTelegramWidget": "برای اتصال از طریق تلگرام وارد شوید",
+      "linkingTelegram": "در حال اتصال تلگرام...",
       "providers": {
         "telegram": "تلگرام",
         "email": "ایمیل",

src/locales/ru.json

@@ -4175,6 +4175,8 @@
       "unlinkError": "Не удалось отвязать аккаунт",
       "goToAccounts": "Привязанные аккаунты",
       "linking": "Привязка аккаунта...",
+      "linkTelegramWidget": "Войдите через Telegram для привязки",
+      "linkingTelegram": "Привязка Telegram...",
       "providers": {
         "telegram": "Telegram",
         "email": "Email",

src/locales/zh.json

@@ -3050,6 +3050,8 @@
       "unlinkError": "取消关联失败",
       "goToAccounts": "关联账户",
       "linking": "正在关联账户...",
+      "linkTelegramWidget": "通过 Telegram 登录以关联",
+      "linkingTelegram": "正在关联 Telegram...",
       "providers": {
         "telegram": "Telegram",
         "email": "邮箱",