Show freshness metadata on shared web cook views

[jongio]

Shared cook views are useful for live monitoring, but a viewer cannot quickly tell when the shared snapshot was created or whether readings are stale.

Acceptance criteria:

• Shared device and archive views show a generated or last-updated timestamp when available.
• Stale readings are visually called out using the existing status styles.
• The change stays within the web package and uses existing UI patterns.

[jongio]

Research refresh: shared cook links are common across ThermoWorks, FireBoard, MEATER, and Combustion style workflows, but stale data is still a trust problem for viewers who are not next to the pit. This issue stays high value because the web app already has health and stale-reading UI patterns that can be reused without new services.

Implementation note: show the page refresh timestamp plus the freshest device or channel reading timestamp, then reuse the existing warning and critical stale styles when the newest reading is old.