`LinkedFileIngestor` should check for `isOnlineLink`

[koppor]

1. Copy https://arxiv.org/abs/2301.00001 into the clipboard
2. Go to Library -> New Entry
3. Choose "Enter Identifier"
4. Click search
5. See the error in the log

2026-06-30 23:00:21 [pool-2-thread-3] org.jabref.logic.ai.ingestion.logic.ingestion.LinkedFileIngestor.ingest()
ERROR: Could not find path for a linked file "https://arxiv.org/pdf/2301.00001v1", while generating embeddings

Reason

@Article{Thompson2023,
...
  file          = {:https\://arxiv.org/pdf/2301.00001v1:PDF},
...
}

JabRef's LinkedFile supports for checking wheterh sth. is online link

[jabref-machine]

👋 Hey @vinisha64, looks like you’re eager to work on this issue — great! 🎉 It also looks like you don't know how to assign issues to yourself. Please read our CONTRIBUTING.md to find out how. It will also guide you in other aspects of contributing to JabRef.

[vinisha64]

/assign-me

[jabref-machine]

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