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/components/AdBanner.svelte

@@ -9,7 +9,7 @@
   } from '../lib/bannerEngine';
   import { defaultBannerTimings, linkify, type BannerHost } from '../lib/banner';
   import type { BannerCampaign, BannerTimings } from '../lib/model';
-  import { onExternalLinkClick } from '../lib/telegram';
+  import { onExternalLinkClick } from '../lib/links';
 
   let {
     campaigns,
@@ -112,7 +112,8 @@
 </script>
 
 <!-- The banner links are rendered via {@html}; a delegated click routes any of them through the
-     Telegram SDK (onExternalLinkClick uses closest('a')) so they skip the WebView confirmation. -->
+     platform opener (onExternalLinkClick uses closest('a')): the Telegram SDK skips the WebView
+     confirmation, the VK away-redirect keeps the Android WebView on the game. -->
 <!-- svelte-ignore a11y_no_static_element_interactions -->
 <!-- svelte-ignore a11y_click_events_have_key_events -->
 <div class="ad" bind:this={viewport} onclick={onExternalLinkClick}>