[SandObserver]

Summary

• Add ui/js/service-link.js with browserLink (a service address as a browser link, or empty for container names, loopback and unparsable values, with credentials, query and fragment dropped) and serviceLink (the Click URL, or that address, plus an optional item path). Pass both to data functions as ctx.browserLink and ctx.serviceLink.
• Treat a widget's Click URL as the service's browser address and build item links on it, falling back to the configured service address.
• Deep link Backup to the Duplicati job log (/ngclient/backup/<id>/log) and the Kopia snapshot list (/snapshots/single-source), Now Playing to the playing item on Plex (machine identifier from /identity, cached per server), Jellyfin, Emby and Navidrome, and System Summary to the Beszel system page.
• Default DNS, Books, Disk Health, GitHub Contributions and System Summary links to their service, NextDNS analytics or the GitHub profile when no Click URL is set.
• Add Click URL fields to System Summary and the Connections map. A press on a chart or a map dot keeps its own behaviour.
• Reword the Click URL hints in all six languages to say what an empty field does.

Testing
All green, Docker build included. Added tests for the link helpers and for the links each data function returns.

Changelog

Added

• Widgets open their service when no Click URL is set, if the browser can reach its address.
• Backup, Now Playing and System Summary open the job, item or system they show, under the Click URL when one is set.
• System Summary and the Connections map have a Click URL setting.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.