feat: Use git submodule for private dependency

- Add wc-licensed-product-client as git submodule in lib/
- Change Composer repository from VCS to path type
- CI now checks out submodules recursively
- Remove COMPOSER_AUTH (no longer needed)

This solves the CI networking issue by fetching the
dependency via git submodule instead of Composer.

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

composer.lock

@@ -4,15 +4,15 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "f7faf49a10004a02b32814806bd51d77",
+    "content-hash": "0c8153ac31232ffe7f0af117cec865b4",
     "packages": [
         {
             "name": "magdev/wc-licensed-product-client",
             "version": "v0.2.2",
-            "source": {
-                "type": "git",
-                "url": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client.git",
-                "reference": "56abe8a97c72419c07a6daf263ba6f4a9b5fe4b1"
+            "dist": {
+                "type": "path",
+                "url": "lib/wc-licensed-product-client",
+                "reference": "f9281ec5fb23bf1993ab0240e0347c835009a10f"
             },
             "require": {
                 "php": "^8.3",
@@ -51,7 +51,9 @@
                 "issues": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client/issues",
                 "source": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client"
             },
-            "time": "2026-01-28T10:56:47+00:00"
+            "transport-options": {
+                "relative": true
+            }
         },
         {
             "name": "psr/cache",