Adds the full Android source tree, Gradle wrapper, fastlane store
metadata and the fdroiddata build recipe so F-Droid can build from
source. README gains build instructions and an updated structure tree.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015g6ECVSKcBG8CJPrqC3G5o
