`theme-init.js` 404s in production, causing dark theme flash

https://oxide.sys.r3.oxide-preview.com/system/silos Just noticed this, ugh. It means the light theme will flash dark first in some browsers. I see it flash in Firefox and Safari but not in Chrome — hopefully most of our users are in Chrome. I thought I made it so `theme-init.js` would end up in the bundle in the right spot, but I must have messed it up.