Bump actions/setup-node from 4 to 7

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 4 to 7.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](https://github.com/actions/setup-node/compare/v4...v7)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/ci.yml

@@ -55,7 +55,7 @@ jobs:
           python-version-file: ".python-version"
           enable-cache: true
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: 24
           cache: npm

Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: build frontend assets (multi-arch: official node image)
-FROM node:26-slim AS assets
+FROM node:24-slim AS assets
 WORKDIR /app
 
 COPY package.json package-lock.json ./