Fix CI job: run on default node image instead of rust:latest

The rust:latest container has no Node.js, but actions/checkout@v4 and
actions/cache@v4 are JS actions that require it to execute at all,
so the job failed before any cargo/fmt steps ran. Use the default
docker runner image and install the Rust toolchain via rustup instead.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.forgejo/workflows/ci.yml

@@ -7,7 +7,6 @@ on:
 jobs:
   ci:
     runs-on: docker
-    container: rust:latest
     steps:
       - uses: actions/checkout@v4
 
@@ -22,8 +21,10 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-cargo-
 
-      - name: Install toolchain components
+      - name: Install Rust toolchain
-        run: rustup component add clippy rustfmt
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --default-toolchain stable --profile minimal --component clippy --component rustfmt
+          echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
 
       - name: Install cargo-make and cargo-audit
         run: |