fix: prefix /engage event paths in search results

[grzdev]

Done

• Prefix /engage event paths with the full Ubuntu URL in search results
• Extract shared logic into _prefix_engage_path helper to avoid duplication
• Ensure consistent behavior between default listing and search results
• Extend existing test to cover /engage path rewriting

QA

• Open the DEMO
• Alternatively, check out this feature branch
• Run the site using the command ./run serve
• View the site locally in your web browser at: http://0.0.0.0:8002/
• Run through the following QA steps
• [List additional steps to QA the new features or prove the bug has been resolved]

Issue / Card

Fixes #

Screenshots

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[webteam-app]

grzdev is not a collaborator of the repo