🎨 Palette: Explicitly highlight keyboard shortcuts with <kbd> tags

[EiJackGH]

💡 What: Wrapped keyboard shortcuts in semantic <kbd> tags with physical key styling and added a text-shadow to the instructions text.
🎯 Why: Improves intuitiveness and discoverability of custom keyboard controls against a dynamic background.
📸 Before/After: Instructions text now visibly stands out as physical keyboard keys.
♿ Accessibility: Uses semantic <kbd> tags for keyboard inputs and text-shadow to maintain high color contrast. Note: Added custom CSS to the internal <style> block to match the file's existing pattern since this is an isolated njk template without external CSS dependencies.

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PR created automatically by Jules for task 2453718479956176999 started by @EiJackGH

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