Prevent failed dynamic import

[saadabdali]

Closes #1002, addressing the recurring PostHog error TypeError: Failed to fetch dynamically imported module.

Dynamic loading is an area where I don't have a ton of expertise, so relied a lot on Claude for assistance figuring out how this works.

Cause, as I understand it:

• Certain assets get a dynamic hashed route with each deploy.
• The app loads a listing of those routes, but fetches the actual modules lazily (only when each one is needed).
• When there's a deploy, the route to each module changes (gets a new hash). If the user doesn't hard-reload, then the next time they need to load an unloaded module, they'll attempt to fetch it from the stale route, causing this error.

Fix: When we hit this preload error, attempt to reload the routes listing.

• we listen for vite:preloadError
• if we hit that error, try to fully reload the page (which should fetch the new URL and then allow us to grab the resource from its updated location)
• track last reload time (to prevent an infinite loop if the resource is actually unloadable)