🎨 Palette: Implement Keyboard Shortcut Toggle for WCAG 2.1.4 Compliance

[ightevenmckane187]

This PR introduces a micro-UX and accessibility enhancement that allows users to enable or disable global keyboard shortcuts.

💡 What:

• Added a "Shortcuts: Enabled/Disabled" button in the footer.
• Added client-side persistent preference tracking via localStorage.
• Added CSS styles to hide visual keyboard shortcut hints (.kb-shortcut) when shortcuts are disabled.
• Updated keydown event listeners to ignore shortcut triggers when shortcuts are disabled.
• Added comprehensive unit tests in tests/server.test.ts to verify correct rendering.

♿ Accessibility:

• Strictly satisfies WCAG 2.1.4 (Character Key Shortcuts) requirements by allowing speech input and keyboard users to completely turn off single-key global shortcuts.
• Added appropriate aria-pressed states and descriptive labels to the toggle button.

---

PR created automatically by Jules for task 2346476964423123389 started by @ightevenmckane187

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.