Fix CI: use python -m pytest explicitly

.gitea/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
           cd app && pip install -e ".[dev]"
       - name: Run tests
         run: |
-          cd app && pytest tests/ -v --cov=src --cov-report=term-missing
+          cd app && python -m pytest tests/ -v --cov=src --cov-report=term-missing
       - name: Check linting
         run: |
           pip install ruff