mvmOS 0.32.0-beta: App identity follows its own manifest, smoother extension popups

Installed apps now take their name, icon and category straight from their own manifest.json at every startup, so a renamed or re-categorized app in the Store picks up the change automatically instead of needing a core update to match it. Browser extension popups also load and resize more smoothly: the page starts fetching as soon as the server address is known instead of waiting on every setting first, and popups no longer fight the browser over their own height — which was cutting off the bottom of lists and dialogs in some extensions. Static app files are now revalidated instead of cached indefinitely, so edits to an app's code show up without a hard refresh. No app version was bumped by this commit; it only touches core.