fix: remove virtual environment from repository and fix code quality checks

- Remove app/.venv from git tracking (should not be committed)
- Update flake8 to only scan project code (app/stiftung, app/core)
- Update black and isort to only check project code
- Update bandit security scanning to only check project code
- Excludes third-party packages that cause linting failures

.github/workflows/code-quality.yml

@@ -27,22 +27,22 @@ jobs:
     - name: Lint with flake8
       run: |
         # Stop the build if there are Python syntax errors or undefined names
-        flake8 app --count --select=E9,F63,F7,F82 --show-source --statistics
+        flake8 app/stiftung app/core --count --select=E9,F63,F7,F82 --show-source --statistics
         # Exit-zero treats all errors as warnings
-        flake8 app --count --exit-zero --max-complexity=10 --max-line-length=88 --statistics
+        flake8 app/stiftung app/core --count --exit-zero --max-complexity=10 --max-line-length=88 --statistics
     
     - name: Check code formatting with black
       run: |
-        black --check app
+        black --check app/stiftung app/core
     
     - name: Check import sorting with isort
       run: |
-        isort --check-only app
+        isort --check-only app/stiftung app/core
     
     - name: Check for security issues
       run: |
         pip install bandit
-        bandit -r app -f json -o bandit-report.json || true
+        bandit -r app/stiftung app/core -f json -o bandit-report.json || true
     
     - name: Upload security report
       uses: actions/upload-artifact@v4