🎨 Palette: Improve V2 navigation and progress bar accessibility

[godie]

This PR introduces several micro-UX and accessibility enhancements focused on the new V2 components and the shared progress bar:

• V2 Navigation Rail: Translated 'Home' to 'Inicio' for Spanish consistency, added aria-label for screen readers, implemented aria-current="page" for active links, and hid decorative icons from the accessibility tree.
• CustomProgressBar: Added standard ARIA attributes (role="progressbar", aria-valuenow, etc.) to ensure progress is correctly announced to assistive technologies.
• V2 Examen Polish: Standardized the loading state by using CustomPreloader instead of plain text and improved icon accessibility with aria-hidden.
• New Tests: Added unit tests for CustomProgressBar to verify the accessibility attributes.
• Lint Fix: Removed an unused React import in V2Landing.jsx.

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PR created automatically by Jules for task 5570955619744467031 started by @godie

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