add balance

server.js

@@ -85,6 +85,11 @@ router.post("/clear-all-sms", (req, res) => {
   res.json({ status: "ok", message: "All messages cleared" });
 });
 
+// GET /balance - get account balance (SMSC API compatible)
+router.get("/balance", (req, res) => {
+  res.json({ balance: "1000.00" });
+});
+
 // Serve static files
 router.use(express.static(path.join(__dirname, "public")));