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>

composer.json

@@ -3,7 +3,7 @@
     "description": "Export database dumps for Shopware 6 environments.",
     "type": "shopware-platform-plugin",
     "license": "MIT",
-    "version": "0.0.5",
+    "version": "0.1.0",
     "keywords": [
         "shopware",
         "shopware6",