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/src/vite-env.d.ts

@@ -9,3 +9,6 @@ interface ImportMetaEnv {
 interface ImportMeta {
   readonly env: ImportMetaEnv;
 }
+
+/** App version string, injected by Vite's define from `git describe` at build time. */
+declare const __APP_VERSION__: string;