feat(landing): VK entry logo + restore the Telegram channel build-arg

Add the VK Mini App logo next to the Telegram one on the landing hero,
linked via the new VITE_VK_APP_LINK build-arg (full URL, wired through
compose, CI and prod-deploy from TEST_/PROD_VITE_VK_APP_LINK).

Also restore the landing's Telegram link itself: commit 57c778f
collapsed the per-language vars to VITE_TELEGRAM_GAME_CHANNEL_NAME in
compose/CI but left gateway/Dockerfile with the stale _EN/_RU ARGs and
without the plain one, so the built bundle saw the var as undefined and
dead-code-eliminated the whole channel-link branch — deployed landings
(prod included) have shown no Telegram logo since.

ui/src/Landing.svelte

@@ -4,7 +4,7 @@
   import { i18n, localeFrom, setLocale, t, type Locale } from './lib/i18n/index.svelte';
   import { loadPrefs, savePrefs, type Prefs } from './lib/session';
   import { aboutContent } from './lib/aboutContent';
-  import { telegramChannelLink } from './lib/landing';
+  import { telegramChannelLink, vkAppLink } from './lib/landing';
 
   // Standalone landing page, the public entry at "/" (the game SPA lives at /app/ and
   // /telegram/). It reuses the app's theme/i18n/prefs leaf modules — not the app store — so it
@@ -17,6 +17,7 @@
 
   const about = $derived(aboutContent(i18n.locale, 24)); // 24h = the auto-match move clock
   const tgLink = $derived(telegramChannelLink());
+  const vkLink = $derived(vkAppLink());
   const locales: { code: Locale; label: string }[] = [
     { code: 'en', label: '🇬🇧 English' },
     { code: 'ru', label: '🇷🇺 Русский' },
@@ -72,10 +73,19 @@
   <section class="hero">
     <h1>{about.title}</h1>
     <p class="tagline">{t('landing.tagline')}</p>
-    {#if tgLink}
-      <a class="tg" href={tgLink} target="_blank" rel="noopener noreferrer" aria-label={t('landing.playTelegram')}>
-        <img src="telegram-logo.svg" alt="" width="64" height="64" />
-      </a>
+    {#if tgLink || vkLink}
+      <div class="entries">
+        {#if tgLink}
+          <a class="entry" href={tgLink} target="_blank" rel="noopener noreferrer" aria-label={t('landing.playTelegram')}>
+            <img src="telegram-logo.svg" alt="" width="64" height="64" />
+          </a>
+        {/if}
+        {#if vkLink}
+          <a class="entry" href={vkLink} target="_blank" rel="noopener noreferrer" aria-label={t('landing.playVK')}>
+            <img src="vk-logo.svg" alt="" width="64" height="64" />
+          </a>
+        {/if}
+      </div>
     {/if}
   </section>
 
@@ -190,19 +200,22 @@
     color: var(--text-muted);
     font-size: 1.05rem;
   }
-  /* The Telegram entry is just the bigger logo (no button chrome, no caption); the link
-     keeps an aria-label for assistive tech. */
-  .tg {
+  /* The platform entries are just the bigger logos in a row (no button chrome, no captions);
+     each link keeps an aria-label for assistive tech. */
+  .entries {
     align-self: center;
-    display: inline-flex;
+    display: flex;
+    gap: 20px;
     margin-top: 8px;
-    border-radius: 50%;
   }
-  .tg img {
+  .entry {
+    display: inline-flex;
+  }
+  .entry img {
     display: block;
     transition: transform 0.12s ease;
   }
-  .tg:hover img {
+  .entry:hover img {
     transform: scale(1.06);
   }
   .info {