fix: add React on Rails pack generation to Rspec CI workflow

- Add bundle exec rails react_on_rails:generate_packs step to Rspec CI
- Resolves missing server-bundle-generated.js error in Rspec builds
- Required for webpack to find generated component registration files

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

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

Author: ihabadham

.github/workflows/rspec_test.yml

@@ -73,6 +73,9 @@ jobs:
       - name: Build i18n libraries
         run: bundle exec rake react_on_rails:locale
 
+      - name: Generate React on Rails packs
+        run: bundle exec rails react_on_rails:generate_packs
+
       - name: Build Rescript components
         run: yarn res:build