Delegate availability persistence to AvailabilityRepository

- Add create() and create_multiple() methods to AvailabilityRepository
- Update AvailabilityService to use repository methods instead of direct db operations

backend/repositories/availability.py

@@ -39,3 +39,28 @@ class AvailabilityRepository:
         await self.db.execute(
             delete(Availability).where(Availability.date == target_date)
         )
+
+    async def create(self, availability: Availability) -> Availability:
+        """
+        Create a new availability record.
+
+        Args:
+            availability: Availability instance to persist
+
+        Returns:
+            Created Availability record (flushed to get ID)
+        """
+        self.db.add(availability)
+        await self.db.flush()
+        return availability
+
+    async def create_multiple(self, availabilities: list[Availability]) -> None:
+        """
+        Create multiple availability records in a single transaction.
+
+        Args:
+            availabilities: List of Availability instances to persist
+        """
+        for availability in availabilities:
+            self.db.add(availability)
+        await self.db.flush()

backend/services/availability.py

@@ -109,14 +109,15 @@ class AvailabilityService:
         await self.availability_repo.delete_by_date(target_date)
 
         # Create new availability slots
-        for slot in slots:
-            availability = Availability(
+        availabilities = [
+            Availability(
                 date=target_date,
                 start_time=slot.start_time,
                 end_time=slot.end_time,
             )
-            self.db.add(availability)
-
+            for slot in slots
+        ]
+        await self.availability_repo.create_multiple(availabilities)
         await self.db.commit()
 
         return AvailabilityDay(date=target_date, slots=slots)
@@ -165,19 +166,22 @@ class AvailabilityService:
 
                 # Copy slots
                 target_slots: list[TimeSlot] = []
-                for source_slot in source_slots:
-                    new_availability = Availability(
+                new_availabilities = [
+                    Availability(
                         date=target_date,
                         start_time=source_slot.start_time,
                         end_time=source_slot.end_time,
                     )
-                    self.db.add(new_availability)
-                    target_slots.append(
-                        TimeSlot(
-                            start_time=source_slot.start_time,
-                            end_time=source_slot.end_time,
-                        )
+                    for source_slot in source_slots
+                ]
+                await self.availability_repo.create_multiple(new_availabilities)
+                target_slots = [
+                    TimeSlot(
+                        start_time=slot.start_time,
+                        end_time=slot.end_time,
                     )
+                    for slot in source_slots
+                ]
 
                 copied_days.append(
                     AvailabilityDay(date=target_date, slots=target_slots)