feat(federation): presence-signing overlay on discovery enable

Enabling Nostr discoverability now opens a signer overlay (same visual
language as the app NIP-07 identity picker) before anything is published:
a locked signer row fixed to the node's discovery key — deliberately not
pickable, personal identities are never used — plus the exact signed
content (DID, npub, software version, kind 30078/NIP-33 format) and a
Sign & Publish confirm. Disabling stays immediate. Also seeds the mock
with discovery OFF to match the production default, and defaults
dwnSyncLabel to 'Unknown' when the backend omits sync_status.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/views/Federation.vue

@@ -212,6 +212,17 @@
       @close="showDiscoverModal = false"
       @sent="loadPendingRequests"
     />
+
+    <PresenceSignModal
+      :show="showPresenceSignModal"
+      :server-name="appStore.serverName"
+      :npub="nodeNpub"
+      :did="selfDid"
+      :version="appVersion"
+      :busy="discoveryToggling"
+      @confirm="confirmPresenceSign"
+      @cancel="showPresenceSignModal = false"
+    />
   </div>
 </template>
 
@@ -230,6 +241,7 @@ import NodeDetailModal from './federation/NodeDetailModal.vue'
 import JoinModal from './federation/JoinModal.vue'
 import PendingRequestsPanel from './federation/PendingRequestsPanel.vue'
 import DiscoverModal from './federation/DiscoverModal.vue'
+import PresenceSignModal from './federation/PresenceSignModal.vue'
 import type { FederatedNode, DwnStatus, SyncResult } from './federation/types'
 import type { PendingPeerRequest } from '@/api/rpc-client'
 import { nodeName, timeAgo } from './federation/utils'
@@ -327,7 +339,7 @@ const dwnSyncLabel = computed(() => {
     case 'synced': return 'Synced'
     case 'syncing': return 'Syncing...'
     case 'error': return 'Error'
-    default: return dwnStatus.value.sync_status
+    default: return dwnStatus.value.sync_status || 'Unknown'
   }
 })
 
@@ -348,6 +360,7 @@ const showDiscoverModal = ref(false)
 // Signing-details disclosure: who signs the presence event (always the node's
 // own discovery key) and a human-readable view of the signed content.
 const showSigningInfo = ref(false)
+const showPresenceSignModal = ref(false)
 const nodeNpub = ref('')
 const appVersion = computed(() => syncStore.serverInfo?.version || '')
 
@@ -378,11 +391,19 @@ async function loadDiscoveryState() {
 }
 
 async function toggleDiscovery() {
+  if (!discoveryEnabled.value) {
+    // Enabling publishes a signed presence event — surface the signer overlay
+    // first so the user sees exactly what gets signed and with which key.
+    // Nothing is published until they confirm.
+    if (!nodeNpub.value) loadNodeNpub()
+    showPresenceSignModal.value = true
+    return
+  }
+  // Disabling publishes nothing new — apply immediately.
   discoveryToggling.value = true
   discoveryError.value = ''
-  const next = !discoveryEnabled.value
   try {
-    const result = await rpcClient.nostrSetDiscovery(next)
+    const result = await rpcClient.nostrSetDiscovery(false)
     discoveryEnabled.value = !!result.enabled
   } catch (e: unknown) {
     discoveryError.value = e instanceof Error ? e.message : 'Failed to toggle discoverability'
@@ -391,6 +412,20 @@ async function toggleDiscovery() {
   }
 }
 
+async function confirmPresenceSign() {
+  discoveryToggling.value = true
+  discoveryError.value = ''
+  try {
+    const result = await rpcClient.nostrSetDiscovery(true)
+    discoveryEnabled.value = !!result.enabled
+    showPresenceSignModal.value = false
+  } catch (e: unknown) {
+    discoveryError.value = e instanceof Error ? e.message : 'Failed to enable discoverability'
+  } finally {
+    discoveryToggling.value = false
+  }
+}
+
 async function loadPendingRequests() {
   try {
     const result = await rpcClient.federationListPendingRequests()