🎨 Palette: Semantic Navigation & Accessibility Improvements

[ISTEC-FOR340]

This PR improves the accessibility and semantic structure of the MySketches landing page and its subprojects. By switching from JavaScript-driven navigation to semantic <a> tags, we enable standard browser features (like opening in a new tab) and improve screen reader compatibility. Additionally, we've added explicit :focus-visible states to provide clear visual affordances for keyboard users.

♿ Accessibility Improvements

• Semantic HTML: Used <a> tags for all navigation elements.
• Focus Indicators: Implemented custom high-contrast focus rings for cards and buttons.
• Language Localization: Ensured lang="es" is correctly set for the target audience.
• Valid Nesting: Converted nested buttons to spans within links to avoid interactive content nesting issues.

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PR created automatically by Jules for task 11892234059163294350 started by @ISTEC-FOR340

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