Fix GitHub Actions workflow to use correct domain

Updated the production build workflow to use developer.repebble.com
instead of developer.rebble.io. This was the missing piece - the
workflow was overriding the config and Dockerfile changes from the
previous commit.

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

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

Author: ericmigi

.github/workflows/build.yml

@@ -122,8 +122,8 @@ jobs:
       - name: Build site
         run: bundle exec jekyll build
         env:
-          URL: https://developer.rebble.io
-          HTTPS_URL: https://developer.rebble.io
+          URL: https://developer.repebble.com
+          HTTPS_URL: https://developer.repebble.com
           JEKYLL_ENV: production
           DOCS_URL: /tmp/docs/
           ALGOLIA_APP_ID: ${{ secrets.ALGOLIA_APP_ID }}