Refine dashboard settings and demo surfaces

[Jamesllllllllll]

Summary

Simplify the dashboard settings experience and polish the related demo and shared app surfaces.

Closes #58.
Related: #14.

What Changed

• Reorganized the dashboard settings page into clearer grouped sections with denser filter controls, updated defaults, and a placeholder official DLC area.
• Tightened the overlay editor so layout, theme, and sizing controls are easier to scan and take up less space.
• Refined shared accent typography and badge styling so headings and small tags stay consistent while keeping the font choice easy to swap later.
• Updated the homepage and account surfaces, including the live/demo streamer presentation and dashboard status layout.
• Switched the Rocksmith demo streamer source to a curated Twitch watchlist with broader tag support as fallback.

How To Test

1. Open /dashboard/settings and verify the settings groups, official DLC placeholder state, and denser overlay controls.
2. Open /dashboard and / and verify the action/status layout, demo toggle behavior, and updated header styling.
3. Load /api/channels/live?source=rocksmith and confirm the demo response prefers the curated live streamers.

Screenshots Or UI Notes

The main visible changes are on the settings dashboard, overlay editor, homepage live/demo section, and dashboard account header.

Checklist

• I tested the change locally
• I updated docs or examples if needed
• I called out any follow-up work or known limitations

[github-actions]

Preview deployment updated.

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