Docs: describe the icon catalogues and the hosts they use

[SandObserver]

Summary

• Rewrite the Icons section on Adding services: four catalogues searched together, alias and spelling matching, the per-result source line, and the light/dark Variant choice.
• Add raw.githubusercontent.com to the outbound host table, and restate what cdn.jsdelivr.net and api.github.com are contacted for.
• State that catalogue indexes are read only while typing in the picker, and never on a dashboard load.
• Quote the import no-change message as the app now writes it, and add the catalogue failure message to the table.
• Re-sync the bundled widget, dashboard and admin code, including the three new scripts.

Testing
npm run build and npm run check both pass. No new tests here; the checks gate links, assets, style and the placeholder domain.

Checklist

• npm run build and npm run check both pass.
• Product UI is shown by running or capturing it, never recreated in CSS.
• Any new preview or screenshot carries no private hostnames or real data.
• Visual changes verified in both colour schemes and both docs themes.
• Links to the app repo still resolve.

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