docs: add GNOME Wayland setup and align desktop FAQs

[setchy]

Summary

• Replace the verbose KDE homepage callout with a subtle Linux Wayland note linking to GNOME and KDE Plasma setup instructions.
• Add a GNOME FAQ covering compatibility, AppIndicator support, extension installation, release bundles, and popup placement.
• Align both desktop FAQs around Requirements, Installation, and Window placement, with reciprocal related links.
• Keep both questions under Troubleshooting rather than introducing a category for only two entries.

Validation

• Biome checks passed for the changed homepage component.
• Matching FAQ structure and setup link targets verified.
• Production build passed with GitHub API calls mocked as unavailable.
• A live build reproduced the existing GitHub API rate-limit hang; the separate API resilience PR addresses it.

This PR contains only homepage and FAQ changes and can be reviewed independently of the API changes.

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Lighthouse	1 paths audited Performance: 92 (🔴 down 1 from production) Accessibility: 100 (no change from production) Best Practices: 100 (no change from production) SEO: 100 (no change from production) PWA: - View the detailed breakdown and full score reports
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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud