Implement foreign key removal before model synchronization in sequelize.js to prevent conflicts during sync. Add error handling and logging for better visibility on foreign key management.

backend/utils/sequelize.js

@@ -490,6 +490,34 @@ const syncModelsAlways = async (models) => {
                     }
                 }
                 
+                // Entferne bestehende Foreign Keys vor dem Sync, damit Sequelize sie nicht aktualisiert
+                try {
+                    const tableName = model.tableName;
+                    const schema = model.schema || model.options?.schema || 'public';
+                    const foreignKeys = await sequelize.query(`
+                        SELECT tc.constraint_name
+                        FROM information_schema.table_constraints AS tc
+                        WHERE tc.constraint_type = 'FOREIGN KEY'
+                        AND tc.table_name = :tableName
+                        AND tc.table_schema = :schema
+                    `, {
+                        replacements: { tableName, schema },
+                        type: sequelize.QueryTypes.SELECT
+                    });
+                    
+                    if (foreignKeys && foreignKeys.length > 0) {
+                        console.log(`  ⚠️  Removing ${foreignKeys.length} existing foreign keys from ${model.name} before sync`);
+                        for (const fk of foreignKeys) {
+                            await sequelize.query(`
+                                ALTER TABLE "${schema}"."${tableName}" 
+                                DROP CONSTRAINT IF EXISTS "${fk.constraint_name}"
+                            `);
+                        }
+                    }
+                } catch (fkError) {
+                    console.warn(`  ⚠️  Could not remove foreign keys for ${model.name}:`, fkError.message);
+                }
+                
                 console.log(`  🔄 Syncing model ${model.name} with constraints: false`);
                 await model.sync({ alter: true, force: false, constraints: false });