Update ChoreFrequency enum: replace adhoc with on_trigger

backend/app/models/chore.py

@@ -7,11 +7,11 @@ import enum
 
 class ChoreFrequency(str, enum.Enum):
     """Chore frequency options."""
+    ON_TRIGGER = "on_trigger"
     DAILY = "daily"
     WEEKLY = "weekly"
     FORTNIGHTLY = "fortnightly"
     MONTHLY = "monthly"
-    ADHOC = "adhoc"
 
 class ChoreStatus(str, enum.Enum):
     """Chore status options."""