ci: run the Node jobs on the version Cypress supports

Cypress 16 declares node ^22 || ^24 || >=26, and both jobs installed it on Node 20, which npm reported as EBADENGINE on every run. Node 25 would match the Dockerfile but falls in the gap between ^24 and >=26.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/workflows/lint.yml

@@ -51,7 +51,7 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: "20"
+          node-version: "24"
           cache: npm
           cache-dependency-path: app/package.json
 

.github/workflows/tests.yml

@@ -153,7 +153,7 @@ jobs:
       - name: Set up Node.js
         uses: actions/setup-node@v4
         with:
-          node-version: "20"
+          node-version: "24"
           cache: npm
           cache-dependency-path: app/package.json