WebUI: Cache server stats for statistics window

This change ensures that the WebUI caches relevant server stats for immediate display once the statistics window is opened. Previously, all stats would remain blank until maindata was fetched. This could take a while if e.g. the user was on the search tab.

Closes #22764.
PR #22817.

src/webui/www/private/scripts/mocha-init.js

@@ -492,7 +492,10 @@ const initializeWindows = () => {
             height: loadWindowHeight(id, 415),
             onResize: window.qBittorrent.Misc.createDebounceHandler(500, (e) => {
                 saveWindowSize(id);
-            })
+            }),
+            onContentLoaded: () => {
+                window.qBittorrent.Statistics.render();
+            }
         });
     };