fix(contacts): create new contacts in the selected address book

[whoalin1]

Summary

Saving a new contact after changing the address-book dropdown created the vCard in the current/default book and then moved it. Activity therefore showed the temporary book instead of the one the user selected.

For unsaved contacts (!dav), move locally into the target book before createVCard so Activity credits the final address book. Existing contacts still update then move.

Closes #5757

Test plan

• Two address books A (default) and B; from All contacts / A, New contact → switch dropdown to B → Save → contact lives in B; Activity says created in B (not A)
• Same flow starting already inside B → Save → Activity still B; no double move
• Edit existing contact in A, change to B, Save → contact moves to B (regression)
• New contact without changing address book → still creates in the expected book

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AI disclosure

This PR was drafted with the help of AI coding assistants (Cursor agents / LLM-based tools), including the description. I am responsible for it and happy to rework anything that doesn't fit.

All commits carry an Assisted-by: Cursor:grok-4.7 trailer.