Unify GitHub Actions workflows and add production deployment support

[cirdes]

Summary

This PR consolidates multiple GitHub Actions workflows into a single unified CI workflow and adds support for deploying to production from the released branch.

Changes

Workflow Consolidation

• Renamed .github/workflows/main.yml → .github/workflows/ci.yml
• Merged verify_components.yml into the main CI workflow as a job
• Removed deploy.yml workflow (Fly.io deployment)

CI Workflow Improvements

• Simplified PR trigger (removed explicit event types)
• Added released branch to push triggers
• Updated actions/checkout from v5 to v6
• Pinned pnpm version to 10.8.0 for consistency
• Simplified test command: bin/rails db:test:prepare test
• Added verify_components job to ensure component generation is up-to-date
• Updated next-deploy job to depend on verify_components

Deployment Enhancements

• Added released-deploy job that deploys to Heroku production (rubyui.git) when pushing to released branch
• Updated next-deploy job name for clarity (deploys to rubyui-next.git)

Dependencies

• Removed dockerfile-rails gem from Gemfile (no longer needed)