- Persist scanner activeCollectionId via shared_preferences
- Restore last selected collection automatically on scan tab load
- Keep selection valid if collection list changes and store fallback safely
- Harden collection membership service rules:
- only owners can invite/remove members
- prevent self-invite duplicates
- block owner removal
- block owner leave action with explicit error
- Improve manage-collection UX with pull-to-refresh and owner leave guidance
