Fix BroadcastReceiver memory leak in scanForWifi

[Lindsor]

Fix BroadcastReceiver memory leak in scanForWifi

Summary

Fixed a critical memory leak in the Android implementation where a BroadcastReceiver was registered in scanForWifi() but never unregistered. The receiver is now properly unregistered after scan results are processed in all code paths:

• After successful scan results are received
• After unsuccessful scan results
• When startScan() returns false (fallback case)

Files changed:

• android/src/main/java/com/lindsor/capacitor/wifi/Wifi.java - Added 3 lines to unregister the receiver

Review & Testing Checklist for Human

This is a YELLOW risk change - the fix is straightforward but I was unable to test on an actual Android device.

• Test wifi scanning on a physical Android device - Verify scanWifi() still works correctly and returns results
• Check for crashes - Monitor logcat for any IllegalArgumentException from attempting to unregister an already-unregistered receiver
• Verify memory leak is fixed - Use Android Profiler to confirm the receiver is being garbage collected after scans
• Test fallback path - Verify the case where wifiManager.startScan() returns false (may require specific device conditions or mocking)

Test Plan

1. Call scanWifi() multiple times in succession (10-20 times)
2. Use Android Profiler to monitor BroadcastReceiver instances - should not accumulate
3. Check logcat for any unregister-related exceptions
4. Verify scan results are still returned correctly

Notes

• I was unable to run the full Android build (npm run verify:android) to verify compilation, only ran TypeScript build and prettier checks which passed
• The fix follows Android best practices for BroadcastReceiver lifecycle management
• This issue was identified as part of a comprehensive efficiency analysis (see EFFICIENCY_REPORT.md for other potential improvements)

Link to Devin run: https://app.devin.ai/sessions/7fcc006dadc142ac80efd3ab5b608a62
Requested by: Marcelo Luz (marcelo.luz@lindsor.com) (@Lindsor)

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