fix(ci): install Node.js in the rust job

actions/checkout@v4 and actions/cache@v4 are JavaScript actions and
require `node` in the container PATH. The rust job in check.yml only
installed system libs and the Rust toolchain, so the post-checkout
cleanup failed with `exec: "node": executable file not found in $PATH`
on every Forgejo run.

The frontend job already installed Node, which is why it succeeded.
The GitHub mirror is unaffected because ubuntu-latest ships with Node
preinstalled.

Validated against the failed run https://git.lacompagniemaximus.com/maximus/Simpl-Resultat/actions/runs/122

.forgejo/workflows/check.yml

@@ -20,16 +20,19 @@ jobs:
       PATH: /root/.cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
       CARGO_TERM_COLOR: always
     steps:
-      - name: Install system dependencies
+      - name: Install system dependencies, Node.js and Rust
         run: |
           apt-get update
           apt-get install -y --no-install-recommends \
             curl wget git ca-certificates build-essential pkg-config \
             libwebkit2gtk-4.1-dev libappindicator3-dev librsvg2-dev libssl-dev
-
-      - name: Install Rust toolchain (stable)
-        run: |
+          # Node.js is required by actions/checkout and actions/cache (they
+          # are JavaScript actions and need `node` in the container PATH).
+          curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
+          apt-get install -y nodejs
+          # Rust toolchain
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain stable --profile minimal
+          node --version
           rustc --version
           cargo --version