chore: apply drupal-extension-scaffold v4.16.1

[Decipher]

Summary

Applies the Drupal Extension Scaffold v4.16.1 to jsonapi_views, providing a complete local development environment, CI/CD pipeline, and code quality tooling.

What's included

• CI/CD: GitHub Actions test workflow (15-matrix lint + test across PHP 8.2-8.5, D10-D11), deploy workflow for Drupal.org mirror
• Local dev: .devtools/ assemble/start/provision scripts, Makefile commands, composer.dev.json dev dependencies
• Code quality: PHPCS, PHPStan, Rector, Twig CS Fixer, ESLint, Stylelint, Prettier, CSpell configs
• Infrastructure: AGENTS.md, Renovate bot, release-drafter, PR template
• Cleanup: Removed .circleci/ in favour of GitHub Actions, updated .gitignore, fixed composer.json validation

Testing

Verified with:

DRUPAL_VERSION=10 make build    # Assembled, started, provisioned
DRUPAL_VERSION=10 make test     # 6/6 PHPUnit tests run (82 assertions)
DRUPAL_VERSION=10 make lint     # All linters configured and runnable

Remaining tasks

• Configure GitHub secrets (DEPLOY_SSH_KEY, DEPLOY_REMOTE, etc.) for Drupal.org mirroring
• Set up branch protection on 8.x-1.x