Add lockfile, dependabot, and improve PDF script reliability

- Add package-lock.json for reproducible builds (npm ci)
- Add dependabot.yml for npm and GitHub Actions updates
- Add .gitignore for node_modules and generated PDF
- Update workflow to use npm ci with caching
- Improve PDF script with proper error handling and HTTP server

.github/dependabot.yml

@@ -0,0 +1,16 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/generate-pdf.yml

@@ -19,9 +19,10 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: '20'
+          cache: 'npm'
 
       - name: Install dependencies
-        run: npm install
+        run: npm ci
 
       - name: Install Playwright Chromium
         run: npx playwright install chromium