CSS regression on staging

[LawnGnome]

For more context, see this thread on Zulip.

Right now on staging (v5005, commit 417f446), there's obvious CSS breakage: links are the wrong colours, the social icons are massive, and various other things just look off. Here's a screenshot:

Using git bisect and building the frontend with pnpm run build hints that the issue began with 139824d, but I'm somewhat dubious about this in practice, since that was in December.

Looking at the CSS being served on staging versus production, it's pretty obvious that there are just a whole bunch of rules and selectors not being included. I haven't had a chance to analyse specifically where the missing rules are coming from to see if there are one or more CSS modules that are obviously missing.

[eth3lbert]

It looks like the nesting rules are all gone.