fix: resolve CI issues - add cd app command and fix F821 ruff warnings

.gitea/workflows/ci.yml

@@ -17,6 +17,7 @@ jobs:
       - name: Run tests and linting
         run: |
           python -m pip install --upgrade pip
+          cd app
           pip install -e ".[dev]"
           python -m pytest tests/ -v --cov=src --cov-report=term-missing
           pip install ruff