feat: Implement a common header component to replace AgentHeader and introduce a new contact page with associated assets.

src/app/(agent)/layout.tsx

@@ -4,7 +4,7 @@ import { useSession } from 'next-auth/react';
 import { useRouter } from 'next/navigation';
 import { useEffect } from 'react';
 import { Footer } from '@/components/layout/Footer';
-import { AgentHeader } from '@/components/layout/AgentHeader';
+import { CommonHeader } from '@/components/layout/CommonHeader';
 
 export default function AgentLayout({
   children,
@@ -43,10 +43,7 @@ export default function AgentLayout({
       <main className="flex-1">
         <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-6">
           {/* Header Bar */}
-          <AgentHeader
-            userName={session?.user?.name}
-            userEmail={session?.user?.email}
-          />
+          <CommonHeader />
 
           {/* Page Content */}
           <div className="mt-6">