mobile: land android follow-ups and ci cache fixes

[dnakov]

Summary

• land Android follow-ups for thread loading, session fork actions, conversation fork flows, account refresh, and voice transcription auth handling
• carry the Android release bindgen workaround into the release workflows
• move release workflow sccache backend env to job scope so compile steps actually use the remote cache

Verification

• ruby -e 'require "yaml"; %w[.github/workflows/ios-testflight.yml .github/workflows/android-play-release.yml .github/workflows/android-apk-release.yml].each { |f| YAML.load_file(f) }; puts "yaml ok"'
• JAVA_HOME="/Applications/Android Studio.app/Contents/jbr/Contents/Home" ./apps/android/gradlew -p apps/android :app:compileDebugKotlin
• git diff --check