Update style, enhance mobile support

wwwroot/css/mobile.css

@@ -1,6 +1,19 @@
 /* === Mobile === */
 @media (max-width: 768px) {
+  #nav {
+    display: none;
+  }
   .msg, .tool-box {
     max-width: 100%;
   }
+  .input-area {
+    margin-bottom: var(--badge-spacing);
+  }
+  .fe-sidebar {
+    width: 100px;
+    min-width: 100px;
+  }
+  .card-grid {
+    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+  }
 }