feat: PWA support + mobile-responsive layout + QR code to open Atlas on phone

Made-with: Cursor

public/manifest.json

@@ -0,0 +1,26 @@
+{
+  "name": "VIBN — Build with Atlas",
+  "short_name": "VIBN",
+  "description": "Chat with Atlas to define your product requirements — anywhere, anytime.",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#f6f4f0",
+  "theme_color": "#1a1a1a",
+  "orientation": "portrait-primary",
+  "icons": [
+    {
+      "src": "/vibn-logo-circle.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "/vibn-logo-circle.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ],
+  "categories": ["productivity", "business"],
+  "lang": "en"
+}