Create a method that deletes all Contact records in a specific Department using DML operations.

Parameters:

• department (String): The Department of contacts to delete

Returns:

• Integer: The number of contacts deleted, or 0 if none found

Requirements:

• Use DML delete operation
• Handle null or empty department by returning 0
• Query contacts by Department before deleting
• Handle DML exceptions gracefully

Example:

Integer deletedCount = deleteContactsByDepartment('Sales');
// Returns: 3 (number of deleted contacts)