ci: bump build timeout to 45m for Puppeteer/Chromium downloads

30m still not enough for EV-12 and EV-13 which download Chromium
during npm install.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 0ca

.github/workflows/build-challenges.yml

@@ -59,7 +59,7 @@ jobs:
     name: "Build ${{ matrix.challenge.name }}"
     needs: discover
     runs-on: ubuntu-latest
-    timeout-minutes: 30
+    timeout-minutes: 45
     strategy:
       # Don't cancel other builds if one fails
       fail-fast: false