chore: enable frontend source maps in Sentry

* Removes unneeded options from TerserPlugin. There is no such option as
  `cache` (this did nothing?), and `parallel` defaults to true.

* Removes an old script that appears to have been previously used to
  upload source maps, but was not referenced anywhere.

.github/workflows/ci.yml

@@ -59,6 +59,8 @@ jobs:
   js-build:
     name: Frontend Build
     runs-on: ubuntu-latest
+    env:
+      SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
     steps:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/setup