refactor backend and persist stock campaign queue

backend/config.js

@@ -0,0 +1,11 @@
+require('dotenv').config();
+
+module.exports = {
+    PORT: process.env.PORT || 3004,
+    API_KEY: process.env.API_KEY || 'nexstar_secret_key_123',
+    ADMIN_EMAIL: process.env.ADMIN_EMAIL || 'admin@admin.com',
+    ADMIN_PASSWORD: process.env.ADMIN_PASSWORD || 'admin123',
+    JWT_SECRET: process.env.JWT_SECRET || 'super_secret_jwt_key_123',
+    DATABASE_URL: process.env.DATABASE_URL || 'postgres://graphuser:graphpassword@localhost:5432/graphdb',
+    N8N_WHATSAPP_TRIGGER_URL: process.env.N8N_WHATSAPP_TRIGGER_URL || 'http://localhost:5678/webhook/whatsapp'
+};