[FEATURE] Add the Form Elements components

Create a set of reusable Razor components for form elements, according to [Bootstrap Italia - Form Elements](https://italia.github.io/bootstrap-italia/docs/form/introduzione/). Components should include Input, Select, Checkbox, Radio, Switch, and support all documented variants and accessibility features.

### Requirements:
- Implement Razor components (e.g., BitInput.razor, BitSelect.razor, BitCheckbox.razor, BitRadio.razor, BitSwitch.razor) for each form element, following Bootstrap Italia styles.
- Support all input types (text, password, email, etc.), select options, checkbox/radio groups, and switches.
- Expose parameters for label, value, validation, and ARIA/accessibility attributes.
- Ensure accessibility best practices are followed.
- Add XML documentation for all public parameters.

### Acceptance Criteria:
- Components render valid Bootstrap Italia markup for each form element.
- All documented variants and features are supported via parameters.
- Components are unit tested for all major variants and use cases.
- Usage examples are provided in the documentation or a sample page.

### References:
- [Bootstrap Italia - Form Elements Documentation](https://italia.github.io/bootstrap-italia/docs/form/introduzione/)