fix: resolve did:dht compilation errors

- Simplify DHT encoding: use JSON instead of DNS packets (drop simple-dns)
- Fix mainline crate API: SigningKey takes 32 bytes, get_mutable returns Result
- Add missing dht_did field to IdentityRecord constructor
- Store DID Document as JSON in DHT (DNS encoding deferred)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/views/Federation.vue

@@ -1,6 +1,15 @@
 <template>
   <div>
-    <div class="hidden md:block mb-8">
+    <div class="mb-8">
+      <button
+        @click="router.push('/dashboard/web5')"
+        class="flex items-center gap-2 text-white/50 hover:text-white/80 transition-colors text-sm mb-4"
+      >
+        <svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 19l-7-7 7-7" />
+        </svg>
+        Back to Web5
+      </button>
       <h1 class="text-3xl font-bold text-white mb-2">Federation</h1>
       <p class="text-white/70">Manage trusted node clusters and sync state across your network</p>
       <p class="text-sm text-white/60 mt-2">{{ nodes.length }} federated node{{ nodes.length !== 1 ? 's' : '' }}</p>
@@ -357,9 +366,12 @@
 
 <script setup lang="ts">
 import { ref, computed, onMounted } from 'vue'
+import { useRouter } from 'vue-router'
 import { rpcClient } from '@/api/rpc-client'
 import NetworkMap from '@/components/federation/NetworkMap.vue'
 
+const router = useRouter()
+
 interface AppStatus {
   id: string
   status: string