Fix GitHub Pages deployment workflow

Updated all GitHub Actions to latest versions to fix deployment failures:
- actions/checkout: v3 → v4
- actions/setup-node: v3 → v4
- actions/configure-pages: v3 → v5
- actions/cache: v3 → v4
- actions/upload-pages-artifact: v2 → v3
- actions/deploy-pages: v2 → v4

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: fguendling

.github/workflows/nextjs.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Detect package manager
         id: detect-package-manager
         run: |
@@ -38,19 +38,19 @@ jobs:
             exit 1
           fi
       - name: Setup Node
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v4
         with:
           node-version: "20"
           cache: ${{ steps.detect-package-manager.outputs.manager }}
       - name: Setup Pages
-        uses: actions/configure-pages@v3
+        uses: actions/configure-pages@v5
         with:
           # Automatically inject basePath in your Next.js configuration file and disable
           # server side image optimization (https://nextjs.org/docs/api-reference/next/image#unoptimized).
           # You may remove this line if you want to manage the configuration yourself.
           static_site_generator: next
       - name: Restore cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             .next/cache
@@ -64,7 +64,7 @@ jobs:
       - name: Build with Next.js
         run: ${{ steps.detect-package-manager.outputs.runner }} next build
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v2
+        uses: actions/upload-pages-artifact@v3
         with:
           path: ./out
 
@@ -77,4 +77,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v2
+        uses: actions/deploy-pages@v4