Fix mobile settings sidebar: keep vertical layout instead of horizontal row

src/web/static/style.css

@@ -787,24 +787,24 @@ body {
     display: block;
 }
 
-/* Mobile: stack sidebar above content */
+/* Mobile: compact vertical sidebar */
 @media (max-width: 640px) {
     .settings-layout {
         flex-direction: column;
     }
     .settings-sidebar {
         width: 100%;
-        flex-direction: row;
-        overflow-x: auto;
+        flex-direction: column;
+        overflow: visible;
         position: static;
         scrollbar-width: none;
+        gap: 1px;
+        padding: 4px;
     }
     .settings-sidebar::-webkit-scrollbar {
         display: none;
     }
     .settings-nav-item {
-        white-space: nowrap;
-        flex-shrink: 0;
         padding: 8px 12px;
         font-size: 0.8rem;
     }