fix: month initialization CTA visibility and template warning flow

[EfeDeveloper]

Summary

• hide 'Iniciar mes' when the month is already initialized from templates\n- keep 'Iniciar mes' available in Gastos when month is empty and not initialized\n- keep no-template feedback as click-time toast only\n- sync and archive OpenSpec change artifacts\n\n## Validation\n- openspec validate --specs\n- manual UI checks on Dashboard and Gastos\n