Implement onboarding reset functionality and enhance backup features

- Added a new method to reset the onboarding state, allowing users to re-initiate the onboarding process.
- Integrated backup creation functionality, enabling users to create encrypted backups of their node identity.
- Updated API endpoints to handle onboarding reset and backup creation requests.
- Enhanced UI components to support the new onboarding reset and backup features, including error handling and user feedback.
- Introduced new dependencies for cryptographic operations and data encoding.

neode-ui/src/views/OnboardingVerify.vue

@@ -14,6 +14,7 @@
 
       <!-- Content Area -->
       <div class="flex flex-col items-center gap-6 mb-6">
+        <p v-if="errorMessage" class="text-red-400 text-sm">{{ errorMessage }}</p>
         <!-- Sign Button (if not verified yet) -->
         <button
           v-if="!verified"
@@ -84,32 +85,35 @@
 import { ref } from 'vue'
 import { useRouter } from 'vue-router'
 import { completeOnboarding } from '@/composables/useOnboarding'
+import { rpcClient } from '@/api/rpc-client'
 
 const router = useRouter()
 const verified = ref(false)
 const isSigning = ref(false)
 const signature = ref('')
+const errorMessage = ref('')
+
+/** Generate a cryptographically random challenge (32 bytes, base64) */
+function generateChallenge(): string {
+  const bytes = new Uint8Array(32)
+  crypto.getRandomValues(bytes)
+  return btoa(String.fromCharCode(...bytes))
+}
 
 async function signChallenge() {
   isSigning.value = true
+  errorMessage.value = ''
 
-  // Simulate signing challenge
-  await new Promise(resolve => setTimeout(resolve, 1500))
-
-  const mockSignature = generateMockSignature()
-  signature.value = mockSignature
-  verified.value = true
-
-  isSigning.value = false
-}
-
-function generateMockSignature(): string {
-  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
-  let result = ''
-  for (let i = 0; i < 128; i++) {
-    result += chars.charAt(Math.floor(Math.random() * chars.length))
+  try {
+    const challenge = generateChallenge()
+    const { signature: sig } = await rpcClient.signChallenge(challenge)
+    signature.value = sig
+    verified.value = true
+  } catch (err) {
+    errorMessage.value = err instanceof Error ? err.message : 'Failed to sign challenge. Please try again.'
+  } finally {
+    isSigning.value = false
   }
-  return result
 }
 
 async function proceed() {