Add git submodule and Gitea CI/CD pipeline for v0.7.2

- Convert wc-licensed-product-client from Composer VCS to git submodule
- Add Gitea Actions workflow for automated releases on version tags
- Update composer.json to use path repository for submodule
- Workflow includes: submodule checkout, PHP setup, translation compilation,
  version verification, package creation, checksum generation, release upload

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

composer.json

@@ -12,14 +12,14 @@
     ],
     "repositories": [
         {
-            "type": "vcs",
-            "url": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client.git"
+            "type": "path",
+            "url": "lib/wc-licensed-product-client"
         }
     ],
     "require": {
         "php": ">=8.3.0",
         "twig/twig": "^3.0",
-        "magdev/wc-licensed-product-client": "dev-main"
+        "magdev/wc-licensed-product-client": "@dev"
     },
     "autoload": {
         "psr-4": {