feat(landing): Russian default + SEO head, icons and OG card

The landing now always opens in Russian (saved 🌐 choice still wins) —
browser-language detection made the indexed content nondeterministic
(Googlebot renders with en-US). landing.html gains the static Russian
SEO head: title/description, canonical pinned to the production origin,
Open Graph card (Telegram/VK link previews), twitter:card, JSON-LD,
theme-color and the favicon set; the SPA shell turns noindex and its
tab title becomes «Эрудит (Скрэббл)». New assets/icons generator
(same tile design as the VK loader) produces favicon.svg/ico,
apple-touch-icon.png and og-image.png into ui/public/, plus robots.txt.

docs/ARCHITECTURE.md

@@ -1099,7 +1099,14 @@ parameters from the URL and the gateway verifies them in-process — §12); a st
 gateway's `/` 308-redirects to `/app/`. The **landing** ships in its own static container: the
 `landing` target of `gateway/Dockerfile` (caddy:2-alpine + the same Vite build,
 `deploy/landing/Caddyfile`) serves it at `/`, so stray public traffic is absorbed by
-static file serving and never reaches the Go edge. Hash-named `/assets/*` are served
+static file serving and never reaches the Go edge. The landing shell carries the site's
+static SEO head — Russian title/description, the Open Graph card (Telegram/VK link
+previews), JSON-LD and a canonical link — with absolute URLs pinned to the production
+origin, so the test contour canonicalises to production instead of being indexed as a
+separate site; the SPA shell is `noindex`, and the landing always boots in Russian (no
+browser-language detection — crawlers render with arbitrary languages). The favicon set,
+`og-image.png` and `robots.txt` ship unhashed from `ui/public/` (generated by
+`assets/icons/`, same tile design as the VK loader). Hash-named `/assets/*` are served
 `immutable` (a relaunch is a cache hit, not a re-download); the HTML shells are
 `no-cache` so a new deploy is picked up — both containers apply the same caching. An
 in-compose **caddy** is the contour's edge: it owns a single `/_gm` Basic-Auth and

docs/FUNCTIONAL.md

@@ -23,7 +23,13 @@ variant's alphabet, remembers answers within the session and rate-limits repeats
 A public **landing page** at the site root introduces the game, switches language and
 theme, and links to the Telegram game channel and the VK Mini App; the game itself runs at
 `/app/` (web), `/telegram/` (the Telegram Mini App) and `/vk/` (the VK Mini App). The landing's theme is ephemeral
-(it follows the system scheme, not the saved preference); its language choice is saved.
+(it follows the system scheme, not the saved preference); its language choice is saved. The
+landing always opens in **Russian** — the browser language is never auto-detected (crawlers
+render with arbitrary languages, so detection would make the indexed content
+nondeterministic); a saved 🌐 choice still wins. The page carries a static Russian SEO head
+(title/description, the Open Graph card Telegram/VK link previews use, a canonical link
+pinned to the production origin, JSON-LD, the favicon set and `robots.txt`), while the SPA
+shell is `noindex` — the landing is the only indexable page.
 
 ### First-run onboarding
 The first time a player opens the app it walks them through the interface with a light

docs/FUNCTIONAL_ru.md

@@ -24,7 +24,14 @@ top-1 подсказку, безлимитную проверку слова с
 Публичная **посадочная страница** в корне сайта представляет игру, переключает язык и
 тему и ведёт в Telegram-канал игры и в VK Mini App; сама игра живёт по адресам
 `/app/` (веб), `/telegram/` (Telegram Mini App) и `/vk/` (VK Mini App). Тема на странице эфемерна (берётся из
-системной настройки, а не из сохранённой), выбор языка сохраняется.
+системной настройки, а не из сохранённой), выбор языка сохраняется. Страница всегда
+открывается на **русском** — язык браузера не определяется автоматически (роботы
+рендерят страницу с произвольным языком, и автоопределение сделало бы
+проиндексированный контент недетерминированным); сохранённый выбор 🌐 по-прежнему
+главнее. Страница несёт статическую русскую SEO-«шапку» (title/description, карточка
+Open Graph, которую используют превью ссылок в Telegram/VK, канонический адрес
+продакшен-домена, JSON-LD, набор favicon и `robots.txt`), а оболочка SPA помечена
+`noindex` — индексируется только посадочная страница.
 
 ### Первый запуск: онбординг
 При первом открытии приложения игрока один раз проводят по интерфейсу лёгким