feat(release): production signing in build.yml + F-Droid metadata filled

- build.yml: use production keystore (KEYSTORE_BASE64) on tag pushes,
  fall back to debug key for PRs/branch builds — build.gradle already
  reads RELEASE_STORE_FILE env var so no Gradle changes needed
- distribution/fdroid-submission/metadata.yml: filled
  AllowedAPKSigningKeys with actual SHA-256 fingerprint, commit tag
  updated to v0.3.1, version bumped to 0.3.1
- app.json: bump version 0.2.3 → 0.3.1, versionCode 1 → 2
- Add eas.json + EAS README for iOS App Store builds
- Add fastlane/metadata/android for Play Store / F-Droid graphics
- Add distribution docs: applestore, fdroid, market, playstore,
  security, threat-model, opencode-site-deploy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -0,0 +1,42 @@
+OpenCode Mobile is a free, open-source (MIT) client for the opencode AI coding agent (sst/opencode). Connect to your self-hosted opencode server and drive AI-powered coding sessions from your phone — no proprietary backend, no mandatory accounts, no tracking by default.
+
+Available on F-Droid and IzzyOnDroid for privacy-conscious users who prefer OSS-only distribution channels. Also available on Google Play with the identical MIT-licensed binary.
+
+KEY FEATURES
+
+• Multiple connection types — local network, secure tunnels (Cloudflare, ngrok), or any self-hosted opencode instance
+• Biometric unlock — fingerprint / Face ID / PIN to keep your sessions private
+• Real-time streaming chat — watch your AI agent think and respond live
+• File diff viewer — see exactly what code changes the agent proposes before you accept
+• Multi-session management — start, resume, and switch between coding sessions
+• Tool call approval — review and approve agent actions before they run on your code
+
+WHO IT'S FOR
+
+• Developers who run opencode (sst/opencode) on their workstation or a server
+• Engineers who want to check in on long-running coding sessions away from their desk
+• Teams who self-host AI dev tools and need a polished mobile companion
+• Privacy-conscious developers who want a mobile coding assistant with zero vendor lock-in
+
+OPEN SOURCE + PRIVACY BY DEFAULT
+
+OpenCode Mobile is MIT licensed. Source code, issue tracker, and community discussion live at:
+https://github.com/dzianisv/opencode-mobile
+
+Crash reporting (Sentry) is opt-in with default OFF. Your code, prompts, and AI responses never leave your own server. The app sends nothing to VIBE TECHNOLOGIES, LLC unless you explicitly enable crash reporting in Settings → Privacy.
+
+SELF-HOSTED FIRST
+
+The app requires you to bring your own opencode server. This is a feature, not a limitation — your AI traffic goes directly to your backend (which can connect to Claude, GPT, Gemini, local models, or any opencode-compatible endpoint). No middleman, no subscription required for core functionality.
+
+An optional opencode Cloud hosted backend is planned as a future paid service for users who prefer not to self-host — but the client will always be free, open, and fully functional without it.
+
+ANTI-FEATURES DISCLOSURE (F-Droid)
+
+NonFreeNet: The opencode server you connect to may in turn connect to proprietary AI services (OpenAI, Anthropic, Google). The app itself contains no proprietary network code and does not require any specific provider.
+
+SUPPORT
+
+Email: support@vibebrowser.app
+Issues: https://github.com/dzianisv/opencode-mobile/issues
+Privacy policy: https://opencode.vibebrowser.app/privacy