Search finds assets by their model name, and booking by model shows what is free

Typing a model's name into the asset search, for example Dell Latitude 5550, used to find nothing unless the name also appeared in each asset's own title, and the asset model view then showed every model with 0 assets. Search now matches the asset model an asset belongs to, in both index modes and in the Shelf Companion app's asset search, which runs on the same server search.

Booking by model from the asset model view got a few improvements too:

• Create new booking shows how many units of each model are free once both dates are set, for example "adding 2 → 2 of 8 available", the same hint Add to existing already gave.
• Asking for more units than a model can give in that window is refused under a clear Not enough units title instead of a generic error.
• The Add to existing booking pickers open on bookings that have not ended yet, soonest first, and list finished bookings after them, most recent first.
• The panel that lists a model's assets keeps its column headers in view while you scroll, and when no asset matches your filters it says how many sit outside them.