Bump actions/setup-node from 4 to 6

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 4 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](https://github.com/actions/setup-node/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build-docker.yml

@@ -35,7 +35,7 @@ jobs:
           fi
 
       # Build Vue 3 frontend
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: '22'
           cache: yarn

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
             # Build Vue frontend & Dependencies
             - name: Set up Node ${{ matrix.node-version }}
               if: steps.django_cache.outputs.cache-hit != 'true'
-              uses: actions/setup-node@v4
+              uses: actions/setup-node@v6
               with:
                   node-version: ${{ matrix.node-version }}
                   cache: "yarn"