The old URLs were glitchy because we weren't escaping the `layerUrls` param… and this will let us take better advantage of the same shared caching as other stuff!
This folder will include code shared by both the client-side app and the server!
The server isn't using it yet, but it will in a new API endpoint soon! I'm doing this in a separate commit to avoid lumping all the import-change noise into that commit.
I'm doing this in preparation for an API endpoint to build outfit images by ID. It'll need the same logic to decide which layers are visible, and the same GQL fragments to load the relevant data!
To help the load time for outfits feel shorter, we now reuse the outfit thumbnail from the Your Outfits page as a placeholder!
This doesn't add any overhead when the thumbnail data _isn't_ in your session cache, e.g. if you navigate to the outfit directly. But if we have the thumbnail on hand already, we just show it, easy peasy!
