Hide visible scrollbar on mobile for a clean, app-like feel

On phones (max-width 767px) the gray scrollbar track is now hidden across the
app (html/body) — swipe-to-scroll still works, only the bar is gone. Desktop
keeps its custom 8px scrollbar unchanged.

Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>

src/index.css

@@ -269,6 +269,21 @@
   background: hsl(var(--muted-foreground) / 0.5);
 }
 
+/* On touch/phone screens, hide the visible scrollbar entirely for a clean,
+   app-like feel. Swipe-to-scroll still works — only the bar is hidden. */
+@media (max-width: 767px) {
+  html,
+  body {
+    scrollbar-width: none; /* Firefox */
+    -ms-overflow-style: none; /* IE/old Edge */
+  }
+  ::-webkit-scrollbar {
+    width: 0;
+    height: 0;
+    display: none; /* Chrome/Safari/WebKit */
+  }
+}
+
 /* Animations */
 @keyframes fadeIn {
   from { opacity: 0; transform: translateY(8px); }