Prevent isRefreshing from getting permanently stuck on fetch errors

[dvdstelt]

Fixes:

• All messages screen doesn't show any messages #2883

Without try/finally, any exception thrown by the fetch function left isRefreshing=true forever, causing all subsequent refreshNow() calls to silently no-op — including the manual Refresh button. Also ensures firstLoad is always cleared so the spinner never shows indefinitely.

Reviewer Checklist

• Components are broken down into sensible and maintainable sub-components.
• Styles are scoped to the component using it. If multiple components need to share CSS, then a .css file is created containing the shared CSS and imported into component scoped style sections.
• Naming is consistent with existing code, and adequately describes the component or function being introduced
• Only functions utilizing Vue state or lifecycle hooks are named as composables (i.e. starting with 'use');
• No module-level state is being introduced. If so, request the PR author to move the state to the corresponding Pinia store.

[johnsimons]

Good catch @dvdstelt.
Although this PR does not address #2883.

Both @PhilBastian and I got pinged by @ramonsmits on #2885 to review it.

We both looked at it and created a separate PR to address the bug.