The official app signs com.rtbishop.look4sat with its own certificate. A fork sharing that applicationId cannot be installed over the official build (signature mismatch) and users saw overwrite/install failures.
- Add applicationId version catalog entry; namespace stays com.rtbishop.look4sat so source imports are untouched, applicationId becomes com.rtbishop.look4sat.bg7nta.
- Update PROPERTY_SATELLITE_DATA_OPTIMIZED meta-data to the fork id.
- Document the fork-applicationId requirement in the version catalog.
Port satlover.de dual-station pass matching feature:
- New feature/mutual module with mutual pass data model
- MutualViewModel: compute overlapping passes for two stations
- ElevationCurveChart: Canvas-based dual elevation curve with drag
- MutualScreen: input form + results with expandable cards
- Navigation: add Mutual tab to bottom navigation bar
- i18n: add Chinese/English strings for new feature