aso(play): keyword-optimize title + short desc, fix dead privacy URL

- title.txt: 'OpenCode Mobile' -> 'OpenCode Mobile: AI Coding' (26/30 chars,
  adds the 'AI coding' search keyword to the strongest Play ranking field)
- short_description: front-load 'AI coding agent for Android' (71/80)
- full_description: dead privacy URL opencode.vibebrowser.app (000) ->
  live dzianisv.github.io/opencode-mobile/privacy/ (200) — was a Play
  rejection risk

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

fastlane/metadata/android/en-US/full_description.txt

@@ -41,4 +41,4 @@ SUPPORT
 
 Email: support@vibebrowser.app
 Issues: https://github.com/dzianisv/opencode-mobile/issues
-Privacy policy: https://opencode.vibebrowser.app/privacy
+Privacy policy: https://dzianisv.github.io/opencode-mobile/privacy/

fastlane/metadata/android/en-US/short_description.txt

@@ -1 +1 @@
-Drive your self-hosted AI coding agent from your phone. MIT. No tracking.
+AI coding agent for Android — drive your self-hosted opencode server.

fastlane/metadata/android/en-US/title.txt

@@ -1 +1 @@
-OpenCode Mobile
+OpenCode Mobile: AI Coding