Improve config flow UX for multi-shade setups

Reuse the home key from already-configured shades so adding subsequent
shades skips the key step. Show human-readable shade names from the hub
in the device picker. Allow selecting multiple shades at once instead of
repeating the flow for each one. Default to hub fetch as the key method.

custom_components/hunterdouglas_powerview_ble/cover.py

@@ -22,7 +22,7 @@ from homeassistant.helpers.device_registry import DeviceInfo, format_mac
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
 
 from .api import CLOSED_POSITION, OPEN_POSITION
-from .const import DOMAIN, HOME_KEY, LOGGER
+from .const import DOMAIN, LOGGER
 from .coordinator import PVCoordinator
 
 
@@ -107,7 +107,7 @@ class PowerViewCover(PassiveBluetoothCoordinatorEntity[PVCoordinator], CoverEnti
     def supported_features(self) -> CoverEntityFeature:  # type: ignore[reportIncompatibleVariableOverride]
         """Flag supported features, disable control if encryption is needed."""
         if (
-            self._coord.data.get("home_id") and len(HOME_KEY) != 16
+            self._coord.data.get("home_id") and not self._coord.api.has_key
         ) or self._coord.data.get("battery_charging"):
             return CoverEntityFeature(0)