Improve visual structure and navigation on various pages

Refactors page titles/descriptions into reusable PageHeader component in AIPage, AnalyticsPage, ChatPage, FinancesPage, FocusPage, SettingsPage, ThemePage, and VoicePage.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: d7e7c4e8-20cb-41c4-9d0e-79f48938fede
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/9777c70b-fc38-4831-8d6b-78dfffe041b0/259ea43b-b9fd-4bd0-b9f3-f4898fd6e25c.jpg

client/src/pages/VoicePage.tsx

@@ -58,12 +58,10 @@ export default function VoicePage() {
       <Sidebar className="w-64 border-r" />
       <div className="flex-1 overflow-auto">
         <div className="p-6">
-          <div className="mb-6">
-            <h1 className="text-2xl font-bold text-gray-900 dark:text-white">Voice Commands</h1>
-            <p className="text-gray-600 dark:text-gray-300">
-              Control your application using voice commands
-            </p>
-          </div>
+          <PageHeader
+            title="Voice Commands"
+            description="Control your application using voice commands"
+          />
 
           <div className="grid grid-cols-1 md:grid-cols-2 gap-6 mb-6">
             {/* Voice Control */}