fix(ui): route external links out of the Android VK WebView

The Android VK client's WebView ignores target=_blank and navigates the
Mini App's own window to the target, stranding the player outside the
game with no way back (the dictionary lookup, About/Feedback links, the
ad banner and the bot-link modal fallbacks). vk-bridge 3.x has no method
to open an external URL, so external links are routed through VK's own
leave-VK redirect (vk.com/away.php), which the client intercepts
natively and hands to the system browser.

onExternalLinkClick moves from lib/telegram to a new lib/links that
composes the Telegram and VK routers; iOS and desktop VK open _blank
correctly and are left alone.

ui/src/screens/About.svelte

@@ -3,7 +3,7 @@
   import { app } from '../lib/app.svelte';
   import { navigate } from '../lib/router.svelte';
   import { aboutContent } from '../lib/aboutContent';
-  import { onExternalLinkClick } from '../lib/telegram';
+  import { onExternalLinkClick } from '../lib/links';
 
   // The auto-match move clock (mirrors backend game.DefaultTurnTimeout = 24h).
   const AUTO_MATCH_HOURS = 24;