Improve apply_subscriptions

Events now have a subscriptions_applied flag. Using apply_subscriptions without passing an event now processes all events in the next week, which have not yet been processed

src/meal_manager/models.py

@@ -33,6 +33,8 @@ class Event(Base):
     team_prep_min: Mapped[int] = mapped_column(default=1, nullable=False)
     team_prep_max: Mapped[int] = mapped_column(default=1, nullable=False)
 
+    subscriptions_applied: Mapped[bool] = mapped_column(default=False, nullable=False)
+
     registrations: Mapped[list["Registration"]] = relationship(
         "Registration", cascade="all, delete"
     )