🎨 Palette: UX Improvements for V2 Exam (Shortcuts & Clipboard)

[godie]

This PR introduces a couple of micro-UX improvements to the V2 Exam interface to make it more intuitive and useful for students.

💡 What:

• Keyboard shortcut (Esc) for exiting the exam session.
• Visual hint [Esc] added to the "Salir" button.
• A new "Copy" button for the "Perla Médica" (Medical Pearl) section with success/error toast feedback.

🎯 Why:

• Frequent users appreciate keyboard shortcuts for navigation.
• Medical pearls contain high-yield information that students often want to save for external notes.

♿ Accessibility:

• Updated aria-label and title for the exit button and the new copy button.
• Ensured decorative icons are hidden from screen readers.
• Maintained consistent Material Design 3 styling.

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PR created automatically by Jules for task 2028307604767111931 started by @godie

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