Backend: Neue API-Endpunkte hinzugefügt

- /api/dashboard/* - Dashboard Übersicht, Cashflow, Steuer-Preview
- /api/customers/* - Kunden CRUD API
- /api/invoices/* - Rechnungen CRUD API + Zahlungen

Server.js angepasst um neue Routen einzubinden.

backend/server.js

@@ -34,6 +34,15 @@ app.use('/uploads', express.static('uploads'));
 // Auth Routes
 app.use('/api/auth', authRoutes);
 
+// Neue API Routen (für Frontend)
+const dashboardRoutes = require('./routes/dashboard');
+const customersRoutes = require('./routes/customers');
+const invoicesRoutes = require('./routes/invoices');
+
+app.use('/api/dashboard', dashboardRoutes);
+app.use('/api/customers', customersRoutes);
+app.use('/api/invoices', invoicesRoutes);
+
 // Nebenkosten Routes laden
 const nebenkostenRoutes = require('./routes/nebenkosten');
 nebenkostenRoutes(app);