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/check-connections.js

@@ -0,0 +1,86 @@
+#!/usr/bin/env node
+
+/**
+ * Script zum Prüfen und Bereinigen von PostgreSQL-Verbindungen
+ */
+
+import './config/loadEnv.js';
+import { sequelize } from './utils/sequelize.js';
+
+async function main() {
+    try {
+        console.log('🔍 Prüfe PostgreSQL-Verbindungen...\n');
+        
+        // Prüfe aktive Verbindungen
+        const [connections] = await sequelize.query(`
+            SELECT 
+                count(*) as total,
+                count(*) FILTER (WHERE state = 'active') as active,
+                count(*) FILTER (WHERE state = 'idle') as idle,
+                count(*) FILTER (WHERE state = 'idle in transaction') as idle_in_transaction,
+                count(*) FILTER (WHERE usename = current_user) as my_connections
+            FROM pg_stat_activity
+            WHERE datname = current_database();
+        `);
+        
+        console.log('📊 Verbindungsstatistik:');
+        console.log(`   Gesamt: ${connections[0].total}`);
+        console.log(`   Aktiv: ${connections[0].active}`);
+        console.log(`   Idle: ${connections[0].idle}`);
+        console.log(`   Idle in Transaction: ${connections[0].idle_in_transaction}`);
+        console.log(`   Meine Verbindungen: ${connections[0].my_connections}\n`);
+        
+        // Prüfe max_connections Limit
+        const [maxConn] = await sequelize.query(`
+            SELECT setting::int as max_connections 
+            FROM pg_settings 
+            WHERE name = 'max_connections';
+        `);
+        console.log(`📈 Max Connections Limit: ${maxConn[0].max_connections}`);
+        console.log(`📉 Verfügbare Connections: ${maxConn[0].max_connections - connections[0].total}\n`);
+        
+        // Zeige alte idle Verbindungen
+        const [oldConnections] = await sequelize.query(`
+            SELECT 
+                pid,
+                usename,
+                application_name,
+                state,
+                state_change,
+                now() - state_change as idle_duration,
+                query
+            FROM pg_stat_activity
+            WHERE datname = current_database()
+            AND state = 'idle'
+            AND state_change < now() - interval '1 minute'
+            ORDER BY state_change ASC
+            LIMIT 10;
+        `);
+        
+        if (oldConnections.length > 0) {
+            console.log(`⚠️  Gefunden ${oldConnections.length} alte idle Verbindungen (> 1 Minute):`);
+            oldConnections.forEach(conn => {
+                console.log(`   PID: ${conn.pid}, User: ${conn.usename}, Idle seit: ${conn.idle_duration}`);
+            });
+            console.log('\n💡 Tipp: Du kannst alte Verbindungen beenden mit:');
+            console.log('   SELECT pg_terminate_backend(pid) FROM pg_stat_activity');
+            console.log('   WHERE datname = current_database() AND state = \'idle\' AND state_change < now() - interval \'5 minutes\';\n');
+        }
+        
+        // Prüfe ob wir nahe am Limit sind
+        const usagePercent = (connections[0].total / maxConn[0].max_connections) * 100;
+        if (usagePercent > 80) {
+            console.log(`⚠️  WARNUNG: ${usagePercent.toFixed(1)}% der verfügbaren Verbindungen werden verwendet!`);
+            console.log('   Es könnte sein, dass nicht genug Verbindungen verfügbar sind.\n');
+        }
+        
+        await sequelize.close();
+        process.exit(0);
+        
+    } catch (error) {
+        console.error('❌ Fehler:', error.message);
+        process.exit(1);
+    }
+}
+
+main();