Add Form Validation Messages

[ryanstpierre]

Description\nImprove client-side validation with helpful error messages for the registration form.\n\n## Tasks\n- Add descriptive error messages for each field\n- Implement real-time validation as users type\n- Show validation errors inline near fields\n- Ensure all required fields are properly marked\n- Add visual indicators for form completion status\n\n## Technical Notes\nConsider using a form validation library or implementing custom validation logic.\n\n## Priority\nMedium