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.

deploy/.env.example

@@ -32,6 +32,7 @@ GM_BASICAUTH_HASH=                     # required; `caddy hash-password` bcrypt
 VITE_TELEGRAM_BOT_ID=
 VITE_TELEGRAM_LINK=                                 # friend-invite Mini App link (full URL, e.g. https://t.me/<bot>/<app>)
 VITE_TELEGRAM_GAME_CHANNEL_NAME=                    # landing "Play in Telegram" link, the bot's game channel
+VITE_VK_APP_LINK=                                   # landing "Play on VK" link (full URL, https://vk.com/app<id>)
 VITE_GATEWAY_URL=
 
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