fix: configure CI database connection properly

- Add dotenv loading to Django settings
- Update CI workflow to use correct environment variables
- Set POSTGRES_* variables instead of DATABASE_URL
- Add environment variables to all Django management commands
- Fixes CI test failures due to database connection issues

app/templates/stiftung/administration.html

@@ -211,6 +211,12 @@
                 </div>
                 <div class="card-body">
                     <div class="row">
+                        <div class="col-md-3 mb-3">
+                            <a href="{% url 'stiftung:app_settings' %}" class="btn btn-outline-primary w-100">
+                                <i class="fas fa-cogs d-block mb-2 fa-2x"></i>
+                                <span>App Settings</span>
+                            </a>
+                        </div>
                         <div class="col-md-3 mb-3">
                             <a href="{% url 'stiftung:audit_log_list' %}" class="btn btn-outline-primary w-100">
                                 <i class="fas fa-history d-block mb-2 fa-2x"></i>