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/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",