fix(dav): handle import components without a UID - #66489

• Ref: Contacts import aborts with TypeError when vCards have no UID (TextImporter structure) #66486

Summary

The import TextImporter stores components that have a UID as a list of instances, but a component without a UID was stored as a single bare instance. ImportService always reads $instances[0] and passes its offsets to extract(), so the first card or event without a UID threw a TypeError and aborted the whole import. This wraps the UID-less entry in a list in the CardDAV and CalDAV text importers and in the xCal importer, which had the same pattern. Such objects now reach the existing "without a UID" handling in importProcess() like any other object, so they are reported per item instead of aborting the import. They are still not imported, since that would need a generated UID and I left that call to you. I added tests for vcf, ical and xcal input.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI