feat: Implement push notification system for admin announcements

- Add a notification manager to handle push notifications and integrate with Nostr events.
- Create a push notification service to manage subscription and permission requests.
- Introduce components for notification settings and permission prompts in the UI.
- Update Nostr store to manage push notification state and enable/disable functionality.
- Enhance NostrFeed to send notifications for new admin announcements.
- Implement test notification functionality for development purposes.

generate-vapid-keys.js

@@ -0,0 +1,36 @@
+#!/usr/bin/env node
+
+// Simple VAPID key generator for testing push notifications
+// In production, you'd want to use proper cryptographic libraries
+
+console.log('🔑 VAPID Key Generator for Push Notifications')
+console.log('')
+
+// Generate a random string for testing
+function generateTestKey(length = 64) {
+  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_'
+  let result = ''
+  for (let i = 0; i < length; i++) {
+    result += chars.charAt(Math.floor(Math.random() * chars.length))
+  }
+  return result
+}
+
+// Generate test VAPID keys
+const publicKey = generateTestKey(87) // Base64 URL-safe, typical length
+const privateKey = generateTestKey(43) // Base64 URL-safe, typical length
+
+console.log('📋 Add these to your .env file:')
+console.log('')
+console.log(`VITE_VAPID_PUBLIC_KEY=${publicKey}`)
+console.log(`VITE_PUSH_NOTIFICATIONS_ENABLED=true`)
+console.log('')
+console.log('⚠️  IMPORTANT: These are test keys for development only!')
+console.log('   For production, generate proper VAPID keys using:')
+console.log('   - web-push library: npx web-push generate-vapid-keys')
+console.log('   - online tool: https://vapidkeys.com/')
+console.log('')
+console.log('🔐 Private key (keep secure, for backend only):')
+console.log(`VAPID_PRIVATE_KEY=${privateKey}`)
+console.log('')
+console.log('✅ Once added, restart your dev server to apply the changes.')