fix(security): reject private and loopback IPs in Telegram DoH fallback (#4129)

Co-authored-by: Maymun <139681654+maymuneth@users.noreply.github.com>

gateway/platforms/telegram_network.py

@@ -135,6 +135,9 @@ def _normalize_fallback_ips(values: Iterable[str]) -> list[str]:
         if addr.version != 4:
             logger.warning("Ignoring non-IPv4 Telegram fallback IP: %s", raw)
             continue
+        if addr.is_private or addr.is_loopback or addr.is_link_local or addr.is_unspecified:
+            logger.warning("Ignoring private/internal Telegram fallback IP: %s", raw)
+            continue
         normalized.append(str(addr))
     return normalized