Add GitHub workflow for PDF generation using Playwright

Create a workflow that generates a DIN A4 PDF of the print version
of index.html and stores it as an artifact. Uses Playwright with
Chromium to load the page, wait for QR codes to render, and
generate the PDF.

.github/workflows/generate-pdf.yml

@@ -0,0 +1,37 @@
+name: Generate PDF Labels
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+  workflow_dispatch:
+
+jobs:
+  generate-pdf:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Install Playwright Chromium
+        run: npx playwright install chromium
+
+      - name: Generate PDF
+        run: npm run generate-pdf
+
+      - name: Upload PDF artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: asn-labels-pdf
+          path: asn-labels.pdf
+          retention-days: 30