feat(FwbInput): Add direct error message support

[countradooku]

• Add errorMessage and successMessage props for direct message support
• Fix slot validation in computed properties ($slots not available in props)
• Add fallback for validation message slots without status
• Implement hideDetails prop to control message visibility
• Maintain backward compatibility with existing slot-based approach

This implementation makes error handling more versatile and similar to other libraries like Vuetify, improving developer experience while preserving existing functionality.

Summary by CodeRabbit

• New Features
  • Enhanced input fields now display clear error and success messages during interactions.
  • Customizable options allow for tailored feedback based on input validations.
  • Introduced a new component showcasing examples of error and success messages for input fields.
  • Added documentation detailing new props for managing validation messages and visibility.