ci: plugin-agnostic PR checks and package-then-release pipeline

- plugin-checks workflow: shopware-cli validate, package + built-JS assertion, phpunit
- release: validate, package from the merge commit, validate the zip, create the release
  via the Gitea API, publish the same zip to the Composer registry
- scripts/protect-main.sh sets required status checks via tea api
- bump to 0.1.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/pr-version-check.yml

@@ -4,6 +4,9 @@ on:
   pull_request:
     branches: [main]
 
+permissions:
+  contents: read
+
 jobs:
   version-changelog:
     runs-on: ubuntu-latest