Add connection management scripts to package.json

- Introduced new scripts: check-connections and cleanup-connections for managing database connections.
- These scripts enhance the backend's ability to monitor and maintain connection health.

backend/cleanup-connections.js

@@ -0,0 +1,55 @@
+#!/usr/bin/env node
+
+/**
+ * Script zum Bereinigen von alten/idle PostgreSQL-Verbindungen
+ */
+
+import './config/loadEnv.js';
+import { sequelize } from './utils/sequelize.js';
+
+async function main() {
+    try {
+        console.log('🧹 Bereinige alte PostgreSQL-Verbindungen...\n');
+        
+        // Beende idle Verbindungen, die älter als 5 Minuten sind (außer unserer eigenen)
+        const [result] = await sequelize.query(`
+            SELECT pg_terminate_backend(pid) as terminated
+            FROM pg_stat_activity
+            WHERE datname = current_database()
+            AND pid <> pg_backend_pid()
+            AND state = 'idle'
+            AND state_change < now() - interval '5 minutes';
+        `);
+        
+        const terminated = result.filter(r => r.terminated).length;
+        console.log(`✅ ${terminated} alte idle Verbindungen wurden beendet\n`);
+        
+        // Zeige verbleibende Verbindungen
+        const [connections] = await sequelize.query(`
+            SELECT 
+                count(*) as total,
+                count(*) FILTER (WHERE state = 'active') as active,
+                count(*) FILTER (WHERE state = 'idle') as idle
+            FROM pg_stat_activity
+            WHERE datname = current_database();
+        `);
+        
+        console.log('📊 Verbleibende Verbindungen:');
+        console.log(`   Gesamt: ${connections[0].total}`);
+        console.log(`   Aktiv: ${connections[0].active}`);
+        console.log(`   Idle: ${connections[0].idle}\n`);
+        
+        await sequelize.close();
+        process.exit(0);
+        
+    } catch (error) {
+        console.error('❌ Fehler:', error.message);
+        if (error.message.includes('SUPERUSER')) {
+            console.error('\n💡 Tipp: Du benötigst Superuser-Rechte oder musst warten, bis Verbindungen freigegeben werden.');
+            console.error('   Versuche es in ein paar Minuten erneut.');
+        }
+        process.exit(1);
+    }
+}
+
+main();