fix(SyncFederationAddressBooks): Reject old tokens to make clients sync from scratch

[marcelklehr]

• resolves: Customer ticket

Summary

0. Tokens on the remote side are deleted if they are older than syncTokensRetentionDays (default 60 days (!) ).
1. The sync kept timing out (30s default). The callers only save the token after the whole loop finishes, so every failed run started again from the same old token.
2. After 60 days, the remote pruned the change history after that token.
3. A later run succeeded and got only the remaining recent changes, plus the current token.
4. Result: status OK, 255 cards, and every later delta builds on that incomplete state.

The WebDAV spec requires that the remote server rejects old tokens, but the implementation in nextcloud currently doesn't do this. This PR fixes the implementation to reject old tokens so the client starts a full sync.

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