P9-9: Deploy to internal Play Store testing

[umwelt]

Estimated: 2h
Dependencies: P9-7

Acceptance Criteria

• App uploaded to Play Store internal testing
• Build passes Google Play review
• Internal testers invited
• Installation available to testers
• Crash reports monitored
• User feedback collected
• Release notes included

Tests

• Testers can install from Play Store
• No crashes reported
• App functions correctly