fix: use 100dvh on html to prevent toolbar/statusbar scroll on mobile

height:100% on html resolves against the layout viewport which on iOS
Safari can include the area behind the address bar and home indicator,
pushing the toolbar off-screen. Using 100dvh (dynamic viewport height)
keeps #app exactly equal to the visible area as browser chrome
shows/hides. The 100% line is retained as a fallback for older browsers.

Author: distantorigin

client/src/app.css

@@ -166,7 +166,11 @@
   padding: 0;
 }
 
-html,
+html {
+  height: 100%;
+  height: 100dvh;
+}
+
 body,
 #app {
   height: 100%;