Fix: Search results stop after first model due to incorrect indentation (#127)

[qzMalekuz]

Summary

Fixes search results returning only for the first model due to incorrect indentation and early return in _xapian_search.

Fixes #127

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Changes

• Moved loop and related logic inside the else block
• Moved return all_results outside the model loop
• Ensured results are aggregated across all models

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Tests

• Added unit test to verify multi-model results
• Mocked external dependencies (xapian, config, object fetch)

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Notes

Manual testing may show no results if search indices are not populated. The test verifies correct behavior.

[qzMalekuz]

Closing this PR in favor of a clean one with minimal commits and no unrelated changes.

New PR: #130 (comment)