fix: bootstrap pip in ci

.gitea/workflows/ci.yml

@@ -32,6 +32,10 @@ jobs:
     needs: hygiene
     steps:
       - uses: actions/checkout@v4
+      - run: |
+          if ! python3 -m pip --version; then
+            python3 -m ensurepip --upgrade || (apt-get update && apt-get install -y python3-pip)
+          fi
       - run: python3 -m pip install -r requirements.txt
       - run: python3 -m compileall app
       - run: python3 -m unittest discover -s tests