Add event-specific guest gift reservations endpoint

Introduced a function `get_event_guest_gift_reservations` in the CRUD layer to fetch gift reservations filtered by event ID. Updated the API endpoint to optionally accept an `event_id` query parameter for retrieving reservations specific to an event.

backend/app/api/routes/events/gifts.py

@@ -1,7 +1,7 @@
 from typing import List, Optional, Dict, Any
 from uuid import UUID
 
-from fastapi import APIRouter, Depends, HTTPException, Path
+from fastapi import APIRouter, Depends, HTTPException, Path, Query
 from sqlalchemy.orm import Session
 
 from app.api.dependencies.auth import get_current_active_user, get_current_user, get_optional_current_user
@@ -1050,19 +1050,25 @@ def read_gift_purchases_by_guest(
     return gift_purchase_crud.get_gift_reservations_by_guest(db, guest_id=guest_id)
 
 @router.get(
-    "/purchases/guest/all",
+    "/reservations/guests",
     response_model=List[GiftPurchase],
-    operation_id="read_guests_gift_purchases"
+    operation_id="read_guests_gift_reservations",
 )
 def read_all_guest_gift_reservations(
         *,
         db: Session = Depends(get_db),
+        event_id: Optional[str] = Query(None, description="Optional event ID to filter reservations by event"),
 ) -> Any:
     """
-    Retrieve all guest gift reservations.
+    Retrieve all guest gift reservations, optionally filtered by event ID.
     """
-    reservations = gift_purchase_crud.get_all_guest_gift_reservations(db=db)
+    if event_id:
+        event_id = UUID(event_id)
+        reservations = gift_purchase_crud.get_event_guest_gift_reservations(db=db, event_id=event_id)
+    else:
+        reservations = gift_purchase_crud.get_all_guest_gift_reservations(db=db)
 
     if not reservations:
         reservations = []
+
     return reservations