Differentiate arrived vs arriving-today in Rooms Accessible View

A confirmed booking for today that hasn't checked in yet is accessible —
staff can get in before the guest arrives. Previously it was lumped with
in-room guests and greyed out.

Backend: classifyBookingStatus() splits NewBook 'staying' bookings by
status string (normalised). Statuses containing 'arriv', 'inhouse' or
'checkedin' → occupied; everything else → arriving. /api/occupancy now
returns both occupied_site_ids and arriving_site_ids.

Frontend:
- Occupied rooms: greyed out + 'Occupied' badge (guest physically in room)
- Arriving today: normal display + amber 'Arrival today' badge (access now,
  prioritise before guest checks in)
- Chip label shows 'Rooms (X free • Y arriving • Z occupied)' breakdown

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api.ts

@@ -84,7 +84,7 @@ export function resolveTask(id: number, body: {
 export function addComment(id: number, note: string, addToTemplate = false): Promise<{ ok: boolean; added_to_template: boolean }> {
   return request(`/tasks/${id}/comments`, { method: 'POST', body: JSON.stringify({ note, add_to_template: addToTemplate }) })
 }
-export function fetchOccupancy(): Promise<{ date: string; occupied_site_ids: string[] }> {
+export function fetchOccupancy(): Promise<{ date: string; occupied_site_ids: string[]; arriving_site_ids: string[] }> {
   return request('/occupancy')
 }