Separate APK releases from develop builds

[fiddur]

The README currently points to APK downloads from the main branch (/releases/download/latest/aurboda.apk) but also references :latest Docker images which come from develop.

This creates confusion about versioning and may lead to version mismatches between the Android app and backend.

Suggested improvements:

1. Create proper versioned releases for stable APK builds
2. Consider semantic versioning for releases
3. Update README to clearly distinguish between:
   • Stable releases (versioned APK + Docker images)
   • Development builds (from develop branch)
4. Consider separate :latest and :develop Docker tags