Previously, if the gateway was unreachable (wrong IP, offline, etc.),
the Android app would crash with an unhandled socket exception.
Changes:
- Wrap socket.connect() in try/catch to handle connection failures
- Return PairResult with error message instead of crashing
- Display actual error message in status text instead of generic 'pairing required'
This gives users useful feedback like 'Connection refused' or
'Network is unreachable' instead of a crash.
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