Bump node from 16 to 21

Bumps node from 16 to 21.

---
updated-dependencies:
- dependency-name: node
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Dockerfile

@@ -39,7 +39,7 @@ RUN . "$NVM_DIR/nvm.sh" && nvm alias default v${NODE_VERSION}
 
 # Build frontend
 ARG BUILDPLATFORM
-FROM --platform=${BUILDPLATFORM} node:16 as frontend
+FROM --platform=${BUILDPLATFORM} node:21 as frontend
 RUN npm install -g @angular/cli
 WORKDIR /build
 COPY [ "package.json", "package-lock.json", "angular.json", "tsconfig.json", "/build/" ]