feat: add functional Settings panel with dark mode and autosave

[TanmayThakur2209]

Summary

This PR implements a functional Settings panel in the Template Playground sidebar. Previously, the Settings button did not perform any action. This change introduces a floating settings panel that allows users to configure appearance and behavior preferences.

Changes

• Added a floating Settings panel near the Settings button using Tailwind CSS
• Implemented Dark Mode toggle synced with global theme state
• Implemented AutoSave toggle to persist template, model, and data in localStorage
• Added Editor Theme selector (Light / Dark / Monaco)
• Ensured Settings panel state updates reactively using Zustand store

Flags

• UI behavior only; no breaking changes introduced
• AutoSave currently persists session data locally (browser storage)
• Feature designed to be extendable for future settings (AI config, debounce time, etc.)

Screenshots or Video

Before:

No.settings.mp4

After:

With.Settings.mp4

Author Checklist

• Ensure you provide a DCO sign-off for your commits using the --signoff option of git commit
• Vital features and changes captured in manual testing
• Commit messages follow AP format
• Extend the documentation, if necessary
• Merging to main from fork:feat/settings-panel in this format

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[TanmayThakur2209]

Hi @dselman

Just a gentle follow-up on this PR. Please let me know if any changes or improvements are needed from my side. I’d be happy to update it.

Thanks!

[mttrbrts]

Thanks for the PR @TanmayThakur2209!

We discussed this PR on a working group call and decided to proceed with an explicit import / export behaviour through our Archive format, rather than any browser-based local storage.

There's a partial PR here.
#562

If we remove auto-save from your new settings dialog, I don't believe that there's much value in duplicating the dark-mode toggle, and adding theming, so I'm going to close the PR.

[TanmayThakur2209]

Thanks for the review and discussion!

That makes sense regarding the Archive-based import/export approach instead of browser localStorage.

I’ll see if there are areas where I can contribute or help extend that functionality.

Looking forward to contributing to the Template Playground.