fix(di): correct provider service FQCNs in services.yaml

Providers were moved into the App\Service\Provider namespace, but
services.yaml still tagged/configured them under the old App\Service
FQCNs, so the _instanceof conditional never matched and the container
failed to compile.

config/services.yaml

@@ -22,21 +22,21 @@ services:
             - '../src/Kernel.php'
 
     _instanceof:
-        App\Service\ProviderInterface:
+        App\Service\Provider\ProviderInterface:
             tags: ['app.provider']
 
-    App\Service\GitHubProvider:
+    App\Service\Provider\GitHubProvider:
         arguments:
             $username: '%env(GITHUB_USER)%'
             $token: '%env(GITHUB_TOKEN)%'
 
-    App\Service\GitLabProvider:
+    App\Service\Provider\GitLabProvider:
         arguments:
             $username: '%env(GITLAB_USER)%'
             $token: '%env(GITLAB_TOKEN)%'
             $baseUrl: '%env(GITLAB_URL)%'
 
-    App\Service\GiteaProvider:
+    App\Service\Provider\GiteaProvider:
         arguments:
             $username: '%env(GITEA_USER)%'
             $token: '%env(GITEA_TOKEN)%'