fix: metadata lookup failure handling

[kevmo314]

Update add method in lib/screens/settings/audio_sources.dart to handle metadata lookup failures.

• Metadata Fetching:

  • Wrap MetadataFetch.extract call with a try/catch block to handle potential exceptions.
  • Assign null to metadata if an exception occurs.
  • Use the URL hostname as the title if metadata lookup fails.

• Audio Source Addition:

  • Update the addSource method to use the title derived from metadata or URL hostname.

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