Start API reservation query 1 day before today to catch in-progress stays

A stay that checked in yesterday only appears on yesterday's date key; querying
from today misses it entirely if the API server doesn't include the checkout date.

custom_components/room_cal_ha/backends/api.py

@@ -34,8 +34,9 @@ class RoomCalApiBackend(ReservationBackend):
   async def async_fetch(self) -> tuple[ReservationData | None, ReservationData | None]:
     session = async_get_clientsession(self._hass)
     today = date.today()
+    start = today - timedelta(days=1)
     end = today + timedelta(days=90)
-    url = f"{self._base_url()}/reservation/{today}/{end}"
+    url = f"{self._base_url()}/reservation/{start}/{end}"
     try:
       async with session.get(url, headers=self._headers()) as resp:
         if resp.status in (401, 403):