test(carddav): refactor testSearch to use clearer assertions and unique UIDs

[joshtrichards]

Summary

Refactors testSearch() and its data provider in CardDavBackendTest to improve clarity and correctness:

• Split $expected into $expectedUris + $expectedNeedles: separates two concerns that were previously mixed into a single tuple array
• Use unique UIDs per VCard (uid-0, uid-1, uid-2): the old shared uid value was invalid per the vCard spec and could mask bugs
• Replace nested loop assertion with direct URI list comparison + per-card assertNotFalse(strpos(...)), giving actionable failure messages instead of a silent count mismatch
• Collapse repetitive property inserts into a $propertyRows loop
• Named keys in data provider entries for readability

No production code changes.

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