Delete external Sass stylesheets

[zackkrida]

Proof of concept to delete all external stylesheets except app.css, previously styles/tailwind.css. This PR has known visual errors, allowed for the purposes of testing. All edited files besides the nuxt config, and the deleted style files will be reverted prior to undrafting this PR. This PR will be the final piece of the legacy style removal milestone.

I really wanted to test this PR for performance, but it seems difficult. I'll have to use the bundle analyzer and compare the css in our main application chunk. I tried extracting all CSS to a single, cacheable CSS file here, because Tailwind's optimizations and purge rules should result in a pretty lean file, but it sadly didn't work. Nuxt doesn't officially support it and the logic I tried to create a single css chunk in nuxt.config.ts resulted in odd errors. Here's the config I added:

{
build: {
  optimization: {
      // Extract CSS to single named file
      splitChunks: {
        cacheGroups: {
          styles: {
            name: 'styles',
            test: /\.(css|vue)$/,
            chunks: 'all',
            enforce: true,
          },
        },
      },
    },
  }
}

[zackkrida]

will undo this.

[zackkrida]

I'm going to close this. Once we implement #1088 this will be quite easy, that's the last instance of this we need to resolve.