Allow numbers to be group names

[GDYendell]

ValidationError: 1 validation error for Group
name
  String should match pattern '^([A-Z][a-z0-9]*)*$' [type=string_pattern_mismatch, input_value='0', input_type=str]
    For further information visit https://errors.pydantic.dev/2.9/v/string_pattern_mismatch