feat(api): keyless unavailable-ranges feed for the guest calendar

GET /api/v1/public/rooms/{id}/unavailable?start=&end= and its RPC twin
chatelet_room_unavailable return the nights a guest cannot book over a
window (default today → +365 d, capped at 400 d): occupying bookings —
live holds included, so the feed always agrees with POST /availability —
and manual blocks, clipped, sorted and coalesced into anonymous half-open
spans. Adjacent spans merge on purpose so a guest cannot tell where one
occupant's dates end and the next begin, nor a block from a stay.

is_available now uses the OCCUPYING_STATUSES constant it was inlining.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

views_api.py

@@ -7,7 +7,7 @@ endpoints (room/block CRUD, settings) are HTTP-only and back the admin UI;
 the guest-facing surface (availability, booking) is what also rides the RPC.
 """
 
-from fastapi import APIRouter, Depends, HTTPException
+from fastapi import APIRouter, Depends, HTTPException, Query
 from lnbits.core.models import WalletTypeInfo
 from lnbits.decorators import require_admin_key, require_invoice_key
 
@@ -24,6 +24,7 @@ from .models import (
     CreateRoomData,
     Room,
     RoomStatus,
+    UnavailableRanges,
     public_booking_dict,
     public_room_dict,
 )
@@ -212,6 +213,20 @@ async def api_public_room(room_id: str) -> dict:
     return public_room_dict(room)
 
 
+@chatelet_api_router.get("/api/v1/public/rooms/{room_id}/unavailable")
+async def api_public_room_unavailable(
+    room_id: str,
+    start: str | None = Query(None, description="YYYY-MM-DD, default today"),
+    end: str | None = Query(None, description="YYYY-MM-DD exclusive, default +365d"),
+) -> UnavailableRanges:
+    """Nights a guest cannot book, merged and anonymous — what a calendar
+    greys out. Keyless, like the room read it hangs off."""
+    try:
+        return await services.get_unavailable_ranges(room_id, start, end)
+    except ValueError as exc:
+        raise _to_http(exc) from exc
+
+
 # --- availability (public read) --------------------------------------------