Remove unused puppeteer dependency

puppeteer was declared in package.json but never imported anywhere in
the codebase -- PDF generation goes through @react-pdf/renderer. Its
postinstall step downloaded a ~150-200MB Chrome build on every clean
`npm ci`, which exhausted the disk on the deploy host and failed the
build with ENOSPC.

That download was wasted work even when it succeeded: the runner stage
never copies /root/.cache/puppeteer out of the builder, so the browser
was discarded when the builder stage ended.

Also drops 633 lines of transitive dependencies from the lockfile.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

package.json

@@ -39,7 +39,6 @@
     "next-auth": "^4.24.14",
     "next-themes": "^0.4.6",
     "pg": "^8.20.0",
-    "puppeteer": "^24.43.1",
     "react": "19.2.4",
     "react-day-picker": "^10.0.0",
     "react-dom": "19.2.4",