Landing v2: icon switchers, ephemeral theme, channel link, drop browser CTA

Owner review-pass rework of the landing page:
- Rename the per-language Telegram link build var
  VITE_TELEGRAM_LINK_EN/_RU -> VITE_TELEGRAM_GAME_CHANNEL_NAME_EN/_RU
  (it carries a channel username; the landing builds https://t.me/<name> --
  the same channels the connector posts to via TELEGRAM_GAME_CHANNEL_ID_*).
- Language switcher -> a globe icon dropdown (flags + names), saved + synced
  to the app prefs.
- Theme switcher -> a sun/moon icon toggle, ephemeral (follows the system
  scheme, no auto, never persisted) -- galaxy-game style.
- Drop the "Play in browser" CTA (no standalone-web onboarding yet).

Docs: FUNCTIONAL(+ru), PLAN, deploy + ui READMEs.

PLAN.md

@@ -1348,6 +1348,12 @@ provided cert) at the contour caddy; prod VPN; rollback.
       timeout (constant reconnects in the caddy log); now an **immediate heartbeat on open** + a **10 s**
       default interval. Both surfaced while diagnosing a reported "slow load in Telegram" that was actually
       the owner's **external network** (the server is sub-ms end-to-end) — not a regression.
+  - **Landing follow-up (owner review pass):** reworked from the first cut — the per-language Telegram
+    link var renamed `VITE_TELEGRAM_LINK_EN/_RU` → **`VITE_TELEGRAM_GAME_CHANNEL_NAME_EN/_RU`** (it carries
+    a channel **username**, the landing builds `https://t.me/<name>`; the connector keeps the matching
+    `..._CHANNEL_ID_..` to post). Switchers became icons — a 🌐 language dropdown (saved, synced to the app)
+    and a ☼/☾ theme toggle that is **ephemeral** (follows the system scheme, never persisted, no "auto").
+    The "Play in browser" CTA was dropped (no standalone-web onboarding yet).
 
 ## Deferred TODOs (cross-stage)