fix: use correct host path for /apps mount in CI workflow

The /apps:/apps mount was incorrect - the runner container has /var/lib/casaos/apps
mounted at /apps, but the job container needs the actual host path. Updated to use
/var/lib/casaos/apps:/apps so the job container can access CI compose files.

.gitea/workflows/pr.yml

@@ -38,7 +38,7 @@ jobs:
       image: docker.notsosm.art/euchre-camp/ci-base:latest
       options: --user root
       volumes:
-        - /apps:/apps
+        - /var/lib/casaos/apps:/apps
 
     steps:
       - name: Checkout code