Stage 17 round 6 (#13/About): About screen content + app version from git describe

- About screen: prominent localized title (Scrabble / Эрудит (Скрэббл)), a rules link
  (en/ru Wikipedia), and the Random-game / Game-with-friends sections; copy lives in a
  shared aboutContent module (the landing will reuse it). The random-game move limit
  inlines the 24h auto-match clock.
- App version: Vite define __APP_VERSION__ from VITE_APP_VERSION (default 'dev'), wired as
  a Docker build-arg sourced from `git describe --tags --always` in the deploy step — no
  manual version bumps. The fallback keeps a plain/local build working.

ui/vite.config.ts

@@ -12,6 +12,12 @@ export default defineConfig(({ mode }) => ({
   // Relative asset base so the one build serves under any path — the gateway maps the
   // Telegram Mini App to /telegram/ (the hash router is path-agnostic).
   base: './',
+  define: {
+    // App version shown on the About screen, injected at build time from `git describe`
+    // via a Docker build-arg (Stage 17). Falls back to "dev" for a plain local/mock build,
+    // so a missing build-arg never breaks the build.
+    __APP_VERSION__: JSON.stringify(process.env.VITE_APP_VERSION || 'dev'),
+  },
   plugins: [svelte()],
   server: {
     port: 5173,