chore(gui-client): make better use of vite as a bundler (#9148)

We already use `vite` as a bundling tool but only to rollup some of the
pre-built files. This setup (and therefore our buildscripts) can be
massively simplified by instructing `vite` to also build our TypeScript
code and compile tailwind.

This makes it much easier to develop locally because one only needs to
run `pnpm vite build --watch` to keep everything up to date.

.github/workflows/_rust.yml

@@ -142,15 +142,8 @@ jobs:
         timeout-minutes: 10
         with:
           runtime: true
-        # These steps must be synchronized with build.sh and build.bat in `rust/gui-client`
-      - name: pnpm install
-        run: |
-          pnpm install
-          cp "node_modules/flowbite/dist/flowbite.min.js" "src/"
-      - name: Compile Tailwind
-        run: pnpm tailwindcss -i src/input.css -o src/output.css
-      - name: Run Vite bundler
-        run: pnpm vite build
+      - run: pnpm install
+      - run: pnpm vite build
       - name: Build client
         run: cargo build -p firezone-gui-client --all-targets
       - uses: taiki-e/install-action@33734a118689b0b418824fb78ea2bf18e970b43b # v2.50.4