feat: CI creates Gitea releases with changelog, app polls for updates on startup

- android-build.yml: fetch full history+tags, embed VITE_APP_BUILD, add step
  to create a tagged Gitea release (build-N) with markdown changelog and APK
  release assets after every push; bump permissions to contents:write
- src/game/update-check.ts: polls Gitea releases/latest, compares build-N tag
  against CURRENT_BUILD (0 in dev), returns UpdateInfo or null; dismissal
  persisted to localStorage
- src/vite-env.d.ts: TypeScript env declarations for VITE_APP_BUILD
- src/scenes/MenuScene.ts: fire-and-forget update check on menu load; renders
  dismissible bottom-bar banner with optional APK download link
- src/game/ai.ts: early-game empty-table dump heuristic (safest card first)

src/vite-env.d.ts

@@ -0,0 +1,10 @@
+/// <reference types="vite/client" />
+
+interface ImportMetaEnv {
+  /** Gitea run number injected at build time by CI (0 in local dev builds). */
+  readonly VITE_APP_BUILD: string | undefined;
+}
+
+interface ImportMeta {
+  readonly env: ImportMetaEnv;
+}