Add a dedicated focus mode to help users enhance concentration and productivity

Implements FocusPage with Pomodoro timer, ambient sounds, and distraction blocking; adds route in App.tsx and sidebar link.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: c5f0c281-8dd8-4846-b452-4a07bcd21062
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/9777c70b-fc38-4831-8d6b-78dfffe041b0/d79f2b79-df7a-44d0-b937-b161f4d6d0d7.jpg

client/src/components/layout/Sidebar.tsx

@@ -18,7 +18,8 @@ import {
   Shield,
   Zap,
   Monitor,
-  UserCheck
+  UserCheck,
+  Focus
 } from "lucide-react";
 
 interface SidebarProps {
@@ -57,6 +58,11 @@ const getNavigation = (t: any) => [
     href: "/ai",
     icon: Brain,
   },
+  {
+    name: t('navigation.focus'),
+    href: "/focus",
+    icon: Focus,
+  },
 ];
 
 const getManagementNavigation = (t: any) => [