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/public/vk-logo.svg

@@ -0,0 +1,11 @@
+<svg width="101" height="100" viewBox="0 0 101 100" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0_2_40)">
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+</g>
+<defs>
+<clipPath id="clip0_2_40">
+<rect width="100" height="100" fill="white" transform="translate(0.5)"/>
+</clipPath>
+</defs>
+</svg>