Fix dark mode toggle navigation reset.

Preserve the currently selected sidebar page when rebuilding the main panel so toggling dark mode no longer jumps users back to Join Meetings.

Made-with: Cursor

meetings_app/ViewController.swift

@@ -1731,7 +1731,8 @@ private extension ViewController {
             applyGoogleProfile(profile)
         }
 
-        showSidebarPage(.joinMeetings)
+        // Preserve the currently selected page during rebuilds (e.g. dark mode toggle).
+        showSidebarPage(selectedSidebarPage)
 
         return panel
     }