fix: stabilize color mapping by using persistent global hash and add SSE heartbeat

backend/index.js

@@ -74,9 +74,15 @@ app.get('/api/stream', (req, res) => {
     // Send initial connection event
     res.write('data: {"connected": true}\n\n');
 
+    // Keep connection alive through Nginx/Cloudflare
+    const keepAlive = setInterval(() => {
+        res.write(':\n\n'); // SSE comment to prevent idle timeout
+    }, 15000);
+
     sseClients.add(res);
 
     req.on('close', () => {
+        clearInterval(keepAlive);
         sseClients.delete(res);
     });
 });

src/pages/Dashboard.tsx

@@ -15,6 +15,17 @@ const COLORS = [
   '#67e8f9', '#f9a8d4', '#fde047', '#a5b4fc', '#5eead4'
 ];
 
+const globalColorMap: Record<string, string> = {};
+let globalColorIndex = 0;
+
+const getProductColor = (name: string) => {
+  if (!globalColorMap[name]) {
+    globalColorMap[name] = COLORS[globalColorIndex % COLORS.length];
+    globalColorIndex++;
+  }
+  return globalColorMap[name];
+};
+
 const formatCurrency = (value: number) => {
   return new Intl.NumberFormat('pt-BR', { style: 'currency', currency: 'BRL' }).format(value);
 };
@@ -75,8 +86,8 @@ const Dashboard = () => {
     const displayProducts = Array.from(new Set([...topSalesNames, ...topRevenueNames])).sort();
     const productColors: Record<string, string> = {};
     
-    displayProducts.forEach((name, index) => {
-      productColors[name] = COLORS[index % COLORS.length];
+    displayProducts.forEach((name) => {
+      productColors[name] = getProductColor(name);
     });
 
     const productsData = topSalesNames.map(name => ({