Fix CI: use working-directory defaults instead of cd commands

.gitea/workflows/ci.yml

@@ -9,6 +9,9 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./app
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
@@ -17,11 +20,10 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          cd app && pip install -e ".[dev]"
+          pip install -e ".[dev]"
       - name: Run tests
-        run: |
+        run: python -m 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
-          cd app && ruff check .
+          ruff check .