Fix CI/CD: Move submodule to lib/ directory like wp-fedistream

- Move submodule from vendor/magdev/ to lib/ to avoid Composer conflicts
- Use relative submodule URL (../wc-licensed-product-client.git)
- Pin submodule to v0.2.2 tag
- Update composer.json with ^0.2 version constraint
- Simplify .gitignore (no vendor exceptions needed)
- Update workflow to exclude lib/.git instead of vendor/.git

Based on working wp-fedistream implementation.

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

.gitea/workflows/release.yml

@@ -97,8 +97,8 @@ jobs:
             -x "${PLUGIN_NAME}/notes.*" \
             -x "${PLUGIN_NAME}/*.po~" \
             -x "${PLUGIN_NAME}/*.bak" \
-            -x "${PLUGIN_NAME}/vendor/*/.git/*" \
-            -x "${PLUGIN_NAME}/vendor/*/CLAUDE.md" \
+            -x "${PLUGIN_NAME}/lib/*/.git/*" \
+            -x "${PLUGIN_NAME}/lib/*/CLAUDE.md" \
             -x "*.DS_Store" \
             -x "*Thumbs.db"