[SandObserver]

Summary

• Stamp each latest() outcome with the time it settled (at), and use it as the entry time.
• Send an Age header (whole seconds since the outcome settled) on successful GET /api/widget-data/:id replies, so a stored result served during a slow refresh states its real age.
• Add readingTime(data) to the widget toolbox: fetchData records now - Age per returned object; anything else reads as now.
• Use it for the toolbox's last-success time in the stale caption and for Weather's "Updated" label.
• Refresh cache-busting stamps for widget-toolbox.js.

Testing
All green. Added tests for the settle time, the Age header on a stored reply, readingTime, and Weather's use of it.

Changelog

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.