Optimize improve performance by using AnyAsync

[tyfndmrl]

• Replaced the AllAsync method with AnyAsync in the BeUniqueTitle method of CreateTodoListCommandValidator.
• This change improves performance by stopping the query as soon as the first matching title is found, rather than checking all records.
• The new implementation checks if any TodoList record has a matching title, which is more efficient, especially for large datasets.

Changes:

• Before:

  return await _context.TodoLists
      .AllAsync(l => l.Title != title, cancellationToken);
  

• After:

  return !await _context.TodoLists
      .AnyAsync(l => l.Title == title, cancellationToken);
  

This optimization enhances performance when validating unique Title values.