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/home.html

@@ -97,7 +97,7 @@
                                     <i class="fas fa-handshake fa-3x text-secondary mb-3"></i>
                                     <h5 class="card-title">🤝 Verpachtungsverwaltung</h5>
                                     <p class="card-text">Organisieren Sie Pachtverträge und deren Verwaltung effizient.</p>
-                                    <a href="{% url 'stiftung:verpachtung_list' %}" class="btn btn-outline-secondary btn-sm mt-2">
+                                    <a href="{% url 'stiftung:land_list' %}" class="btn btn-outline-secondary btn-sm mt-2">
                                         <i class="fas fa-external-link-alt me-1"></i>Öffnen
                                     </a>
                                 </div>
@@ -143,7 +143,7 @@
                         <a href="{% url 'stiftung:paechter_list' %}" class="btn btn-info btn-lg">
                             <i class="fas fa-user-tie me-2"></i>Pächter
                         </a>
-                        <a href="{% url 'stiftung:verpachtung_list' %}" class="btn btn-secondary btn-lg">
+                        <a href="{% url 'stiftung:land_list' %}" class="btn btn-secondary btn-lg">
                             <i class="fas fa-handshake me-2"></i>Verpachtungen
                         </a>
                         <a href="{% url 'stiftung:foerderung_list' %}" class="btn btn-warning btn-lg">