Implemented proper BLE cleanup mechanism on user logout:
**Root Cause:**
- BLE cleanup callback was being set but reference could become stale
- No explicit cleanup call in profile logout handler
- Callback stability issues due to re-renders
**Changes:**
1. app/_layout.tsx:
- Use useRef pattern to maintain stable callback reference
- Set callback once with ref that always points to current cleanupBLE
- Cleanup callback on unmount to prevent memory leaks
2. app/(tabs)/profile/index.tsx:
- Add explicit cleanupBLE() call in logout handler
- Import useBLE hook to access cleanup function
- Ensure cleanup happens before logout completes
3. services/api.ts:
- Update setOnLogoutBLECleanupCallback signature to accept null
- Allows proper cleanup of callback on unmount
4. jest.setup.js:
- Add AsyncStorage mock to prevent test failures
5. Tests:
- Add comprehensive BLE cleanup tests
- Test callback pattern and stability
- Test logout flow with BLE cleanup
- Test error handling during cleanup
**Result:**
BLE connections now properly disconnect when user logs out,
preventing stale connections and potential resource leaks.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
