Trigger a page refresh if a new version is available

[dixhuit]

On detection of initial page activity, request the latest app version from the backend. If the returned value is greater than the client's current value, force a page refresh (which in turn will get the latest app version and trigger any required updates).

Consider caching the returned value and checking that first. Bust the cache every so often (30mins?).

UPDATE: Probably better to just upgrade UC to be a PWA and use service worker caching.