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.

src/lib/nostr/identity.ts

@@ -1,5 +1,5 @@
 import { generateSecretKey, getPublicKey, nip19 } from 'nostr-tools'
-import { SecureStorage, type EncryptedData } from '@/lib/crypto/encryption'
+import { SecureStorage } from '@/lib/crypto/encryption'
 import { bytesToHex, hexToBytes } from '@/lib/utils/crypto'
 
 export interface NostrIdentity {