- Dashboard: replace Assign link with device dropdown + arrow button for
quick inline assignment without leaving the page
- Device detail: replace hardcoded 4-row install form with 1 row + '+ Add
brand' button that clones rows dynamically
- Device detail: add 'Install Specific Battery' card with dropdown of all
available batteries (label, brand, size, notes) via new /device/<id>/install-one route
- Tests: 4 new acceptance tests covering dashboard quick-assign and
install-one, including capacity enforcement on both paths (39 total)