refactor: improve nostr connection and message handling

- Add WebSocket manager class for better connection handling
- Split message handling into separate store
- Add encryption service class
- Create chat composable for reusable chat logic
- Add error handling service
- Add connection status indicators throughout app
- Add message persistence service
- Improve subscription reliability with EOSE handling
- Add connection state management
- Hide status text on mobile for better space usage

These changes improve code organization, reliability, and user experience by:
- Better separation of concerns
- More robust error handling
- Clearer connection status feedback
- Improved message persistence
- More maintainable WebSocket management
- Better mobile responsiveness

Breaking changes:
- Message handling moved to separate store
- WebSocket connections now managed through NostrWebSocketManager
- Encryption now handled through NostrEncryption service

src/composables/useChat.ts

@@ -0,0 +1,23 @@
+export function useChat(pubkey: string) {
+  const messageStore = useMessageStore()
+  const nostrStore = useNostrStore()
+  
+  const messages = computed(() => 
+    messageStore.messages.get(pubkey) || []
+  )
+
+  const sendMessage = async (content: string) => {
+    if (!content.trim()) return
+    await nostrStore.sendMessage(pubkey, content)
+  }
+
+  const loadHistory = async () => {
+    await nostrStore.subscribeToMessages()
+  }
+
+  return {
+    messages,
+    sendMessage,
+    loadHistory
+  }
+}