Update actions/setup-node action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -15,7 +15,7 @@ jobs:
         fetch-depth: '0'
 
     - name: Setup Node.js
-      uses: actions/setup-node@v5
+      uses: actions/setup-node@v6
       with:
         node-version: '24'
 

.github/workflows/webapp-dev.yml

@@ -9,7 +9,7 @@ jobs:
       uses: actions/checkout@v6
 
     - name: Setup Node.js
-      uses: actions/setup-node@v5
+      uses: actions/setup-node@v6
       with:
         node-version: '24'