Adds PUT /api/collections/{id}/custom-order support (updateCollectionCustomOrder)
and a reorder mode in ManualItemsView: loads every page of a manual collection
(so the wholesale-replace PUT never drops items), lets the user move items with
up/down icon buttons, and saves/cancels. Reorder is offered for any manual
collection with useCustomPlaybackOrder on, not just movies-only (server/enumerator
already support any kind).
Widens the add-items picker (ADDABLE_TYPE_LIST, MEDIA_KIND_FILTERS,
toAddItemsRequest) from 4 to all 10 addable media kinds; the default "All" search
fan-out stays Movie/Show/Artist (seasons excluded per #180), with the new kinds
reachable via their specific filter, mirroring Blazor's per-kind list pages.
timothy
606d50bb8d