feat: Implement comprehensive Nostr identity and social features

## Core Identity Management
- Add secure key generation and import functionality
- Implement AES-GCM encryption with PBKDF2 key derivation
- Create password-protected identity storage
- Add browser-compatible crypto utilities (no Buffer dependency)

## User Interface
- Build identity management dialog with tabs for setup and profile
- Add navbar integration with user dropdown and mobile support
- Create password unlock dialog for encrypted identities
- Integrate vue-sonner for toast notifications

## Nostr Protocol Integration
- Implement event creation (notes, reactions, profiles, contacts)
- Add reply thread detection and engagement metrics
- Create social interaction composables for publishing
- Support multi-relay publishing with failure handling
- Add profile fetching and caching system

## Security Features
- Web Crypto API with 100k PBKDF2 iterations
- Secure random salt and IV generation
- Automatic password prompts for encrypted storage
- Legacy support for unencrypted identities

## Technical Improvements
- Replace all Buffer usage with browser-native APIs
- Add comprehensive error handling and validation
- Implement reactive state management with Vue composables
- Create reusable crypto utility functions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/App.vue

@@ -1,14 +1,47 @@
 <script setup lang="ts">
-import { onMounted, onUnmounted } from 'vue'
+import { onMounted, onUnmounted, ref } from 'vue'
 import Navbar from '@/components/layout/Navbar.vue'
 import Footer from '@/components/layout/Footer.vue'
 import ConnectionStatus from '@/components/nostr/ConnectionStatus.vue'
+import PasswordDialog from '@/components/nostr/PasswordDialog.vue'
+import { Toaster } from 'vue-sonner'
 import { useNostr } from '@/composables/useNostr'
+import { identity } from '@/composables/useIdentity'
+import { toast } from 'vue-sonner'
 
 const relays = JSON.parse(import.meta.env.VITE_NOSTR_RELAYS as string)
 const { isConnected, isConnecting, error, connect, disconnect } = useNostr({ relays })
 
+const showPasswordDialog = ref(false)
+
+async function handlePasswordUnlock(password: string) {
+  try {
+    await identity.loadWithPassword(password)
+    showPasswordDialog.value = false
+    toast.success('Identity unlocked successfully')
+  } catch (error) {
+    toast.error('Failed to unlock identity. Please check your password.')
+  }
+}
+
+function handlePasswordCancel() {
+  showPasswordDialog.value = false
+}
+
 onMounted(async () => {
+  // Check if we have an encrypted identity that needs password
+  if (identity.hasStoredIdentity() && identity.isStoredIdentityEncrypted()) {
+    showPasswordDialog.value = true
+  } else {
+    // Initialize identity system for non-encrypted identities
+    try {
+      await identity.initialize()
+    } catch (error) {
+      console.error('Failed to initialize identity:', error)
+    }
+  }
+  
+  // Connect to Nostr relays
   await connect()
 })
 
@@ -39,5 +72,17 @@ onUnmounted(() => {
 
       <Footer />
     </div>
+
+    <!-- Toast notifications -->
+    <Toaster />
+
+    <!-- Password unlock dialog -->
+    <PasswordDialog
+      v-model:is-open="showPasswordDialog"
+      title="Unlock Identity"
+      description="Your Nostr identity is encrypted. Enter your password to unlock it."
+      @password="handlePasswordUnlock"
+      @cancel="handlePasswordCancel"
+    />
   </div>
 </template>