Fix test assertion for updated error message

- Updated test to match new descriptive error message format
- Changed from 'not within available' to 'not within any available time ranges'
- All tests now passing

backend/tests/test_booking.py

@@ -299,7 +299,7 @@ class TestCreateBooking:
             )
         
         assert response.status_code == 400
-        assert "not within available" in response.json()["detail"]
+        assert "not within any available time ranges" in response.json()["detail"]
 
 
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