Fix: Personal Space memories now visible again

Personal Space memories were hidden after the #233 upgrade: Topic cards showed the correct memory count (e.g. "57") but opening a Topic listed nothing. The cause was a missing acceptance timestamp on the personal vault membership row — the security check that gates direct memory queries requires it, while the count-returning RPCs bypass it. This migration backfills the timestamp on all existing personal memberships and updates the provisioning function so new users are never affected.