feat(lxlweb): make library fetching more robust; warm up caches on startup

[andersju]

Previously, if startRefreshLibraries failed (for example, because the EMM API was unavailable), lxlweb would run with no library/org data for at least 12 hours (until a regularly scheduled refresh succeeded).

This PR does a couple things:

• Loading/caching of libraries/orgs/util is done immediately at start-up instead of when the first request comes in (but it deliberately still doesn't block any requests if loading hasn't finished).
• If the initial refreshLibraries fails, it keeps trying every 30 seconds instead of waiting for 12 hours. Only after a successful fetch does it schedule the 12-hour refresh interval.

Related to #1649

[johanbissemattsson]

LGTM!

A slightly more SvelteKit_ish_ way would be using an init hook but it should be no different than writing the initialisation logic at the top level of the module.

[andersju]

LGTM!

A slightly more SvelteKit_ish_ way would be using an init hook but it should be no different than writing the initialisation logic at the top level of the module.

Good point! I adjusted it a bit.

[johanbissemattsson]

🙌