refactor(frontend): reorder sidebar — messages first, voice below

Default tab is now 'messages'; Voice & Media moved below
Messages in both desktop sidebar and mobile tab bar.
Updated Header titles/subtitles to match new order.

Co-Authored-By: Claude <noreply@anthropic.com>

services/frontend/src/widgets/Sidebar.tsx

@@ -9,8 +9,8 @@ import { MascotImage } from "./mascot/MascotImage";
 
 const navItems: Array<{ id: DashboardTab; label: string; icon: typeof Radio }> =
   [
-    { id: "live", label: "Live", icon: Radio },
-    { id: "messages", label: "Messages", icon: MessageSquare },
+    { id: "messages", label: "Messages & Moderation", icon: MessageSquare },
+    { id: "live", label: "Voice & Media", icon: Radio },
     { id: "dashboard", label: "Dashboard", icon: LayoutDashboard },
   ];