chore(deps): bump actions/setup-node from 4 to 6 (#1125)

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 4 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Naomi Most <naomi.most@orkes.io>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -321,7 +321,7 @@ jobs:
       - uses: actions/checkout@v6
 
       - name: Set up Node
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: "22"
           cache: "yarn"

.github/workflows/publish-next.yaml

@@ -52,7 +52,7 @@ jobs:
 
       # ── UI (ui-next) ─────────────────────────────────────────────────────────
       - name: Set up Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: '22'