Add web push notification system for user engagement and updates

Implement a web push notification system, including service worker integration, user subscription management, and an admin interface for sending broadcast messages.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 23852c00-4779-460a-9e0c-d09fee4b6c92
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: f585829f-898b-492f-82a5-11f4a76c87fb
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/f209e72a-0939-48fa-84fc-57854de71967/23852c00-4779-460a-9e0c-d09fee4b6c92/ICRgny1
Replit-Helium-Checkpoint-Created: true

client/src/components/header.tsx

@@ -3,6 +3,7 @@ import { Menu, X, Search } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { useState, useRef, useEffect } from "react";
 import folxLogo from "@assets/folx_MT_poz_b_1772296729169.png";
+import PushNotificationBell from "./push-notification-bell";
 
 const navItems = [
   { label: "Start", href: "/" },
@@ -63,6 +64,7 @@ export default function Header() {
           </nav>
 
           <div className="flex items-center gap-2">
+            <PushNotificationBell />
             {searchOpen ? (
               <form onSubmit={handleSearch} className="flex items-center gap-1" data-testid="form-header-search">
                 <input