Add per-child all-done and present-today binary sensors

all_done is on exactly when the child owed quests today and owes none
remaining (a zero-quest day stays off so celebrations never fire on
an empty day); present_today mirrors the presence engine's answer
for the HA-local date.

custom_components/nestquest/const.py

@@ -8,8 +8,8 @@ LOGGER_NAME = "custom_components.nestquest"
 LOGGER = logging.getLogger(LOGGER_NAME)
 
 # Platforms set up per config entry (Feature 10): the per-child day
-# sensors. binary_sensor joins when task 4's entities land.
-PLATFORMS: list[str] = ["sensor"]
+# sensors and binary sensors.
+PLATFORMS: list[str] = ["sensor", "binary_sensor"]
 
 #: Canonical domain-global service names (design/ENTITIES-AND-SERVICES.md §2
 #: plus the existing Feature 07 regenerate service).