Improve scan_for_virus robustness and add missing resource test

[dikshaa2909]

Issues

• Closes: scan_for_virus with ClamAV docker container failed: CodebaseResource matching query does not exist #2019

Changes

This improves the robustness of scan_for_virus when ClamAV reports files that are not indexed in CodebaseResource.

Previously, .get(path=...) could raise DoesNotExist, causing the pipeline to fail when ClamAV returned a file not present in the database.

This change:

• Avoids exception-driven control flow
• Preloads indexed resource paths to prevent per-file DB lookups
• Safely skips non-indexed infected files
• Preserves existing virus detection behavior
• Fixes typo in extra_data key (calmav → clamav)
• Adds a regression test covering the missing-resource scenario

Checklist

• I have read the contributing guidelines
• I have linked an existing issue above
• I have added unit tests covering the new code
• I have reviewed and understood every line of this PR

[dikshaa2909]

Hi @tdruez @pombredanne can you pls review !!

[dikshaa2909]

Hi @tdruez @pombredanne can u pls review it when u have time ! Thanks !