Run app tests in the builder image

- Set testing image to ubi9/python-311
- Skip installing packages which are already present in the image

Fixes #313

Assisted-by: Claude Code

.forgejo/workflows/ci.yml

@@ -29,11 +29,10 @@ jobs:
           - 3000:3000
     container:
       # This is chosen to match our production environment
-      image: quay.io/almalinuxorg/almalinux:9
+      image: registry.access.redhat.com/ubi9/python-311
     steps:
-      - name: Install Python, nodejs, git, and build dependencies
-        run: dnf -y install nodejs git python3.11 python3.11-pip python3.11-setuptools-wheel
-          python3.11-setuptools krb5-devel python3.11-devel gcc sqlite-devel
+      - name: Install setuptools
+        run: dnf -y install python3.11-setuptools-wheel python3.11-setuptools
       - name: Check out the project source
         uses: actions/checkout@v6
         with: