Improve inspect page

[shu8]

This PR:

• wires up the import buttons to update the UI on import
• wires up the update manifest button to actually update it
• moves the import flow to a separate screen
• finished wiring up the bake button
• UX improvements
  • 'trickling' progress bars during long tasks
  • rename Export tab to Actions
  • disable the 'add file' button until a file is uploaded

A demo of what it looks like now:

[avaer]

Just gotta say, screencaps in PRs are amazing.

[avaer]

Is this branch up to date with master? I still see the weird design.

[avaer]

~This states that you can browse packages to inspect but you actually can't do that from the browse page.~

~Imo the browse page needs major improvements, one of them being the ability to inspect packages intuitively (right now the UI for moving forward from a package to the next page is really confusing).~

EDIT: ok so you can inspect, by clicking the non-ui portions of the packages on the browse page. This is still pretty confusing with the inline dropdowns. I think we need to make the UI portions of the browse page packages much clearer that it's UI.

Those links should either be buttons or an overlay on top of the package card or something, because they don't seem like links at all. It is also not clear that the package card is clickable into the inspect page. Maybe we don't need these inline links at all, if they are adding to the confusing UI.

The original Exokit site also has an items-based concept for package UI design which we could use on the browse page (it's similar to the one we use here in edit.html).

Anyway, this is more of a tangent. I'll break it out to a separate issue: https://github.com/webaverse/xrpackage/issues/91

[shu8]

Sounds good thanks -- was just about to rebase 😅