feat(app): add Nostr feed integration with real relay connections

Create useNostr composable with raw WebSocket connections to public
relays (relay.damus.io, nos.lol, relay.snort.social). Subscribe to
kind:1 notes with limit 50. Update NostrGrid to use real data instead
of mock notes. Lazy-load on tab activation, clean disconnect.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/composables/useNostr.ts

@@ -0,0 +1,191 @@
+import { ref, shallowRef, onUnmounted } from 'vue'
+
+export interface NostrEvent {
+  id: string
+  pubkey: string
+  kind: number
+  content: string
+  created_at: number
+  tags: string[][]
+  sig: string
+}
+
+export interface NostrNote {
+  id: string
+  pubkey: string
+  authorName?: string
+  nip05?: string
+  kind: number
+  content: string
+  created_at: number
+  tags: string[][]
+}
+
+interface RelayState {
+  url: string
+  ws: WebSocket | null
+  connected: boolean
+}
+
+const RELAYS = [
+  'wss://relay.damus.io',
+  'wss://nos.lol',
+  'wss://relay.snort.social',
+]
+
+const events = shallowRef<NostrNote[]>([])
+const isConnected = ref(false)
+const relayStates = ref<{ url: string; connected: boolean }[]>(
+  RELAYS.map(url => ({ url, connected: false }))
+)
+
+let relays: RelayState[] = []
+let subscriptionId: string | null = null
+let initialized = false
+
+function generateSubId(): string {
+  return 'aiui-' + Math.random().toString(36).slice(2, 10)
+}
+
+function truncatePubkey(pubkey: string): string {
+  if (pubkey.length <= 12) return pubkey
+  return pubkey.slice(0, 8) + '...' + pubkey.slice(-4)
+}
+
+function parseEvent(data: unknown): NostrEvent | null {
+  if (!Array.isArray(data)) return null
+  // NIP-01: ["EVENT", <subscription_id>, <event>]
+  if (data[0] !== 'EVENT' || !data[2]) return null
+  const evt = data[2]
+  if (!evt.id || !evt.pubkey || typeof evt.kind !== 'number' || typeof evt.content !== 'string') {
+    return null
+  }
+  return evt as NostrEvent
+}
+
+function addEvent(evt: NostrEvent) {
+  // Deduplicate by ID
+  const existing = events.value.find(e => e.id === evt.id)
+  if (existing) return
+
+  const note: NostrNote = {
+    id: evt.id,
+    pubkey: evt.pubkey,
+    authorName: truncatePubkey(evt.pubkey),
+    kind: evt.kind,
+    content: evt.content,
+    created_at: evt.created_at,
+    tags: evt.tags ?? [],
+  }
+
+  // Insert sorted by created_at (newest first)
+  const newEvents = [...events.value, note]
+    .sort((a, b) => b.created_at - a.created_at)
+    .slice(0, 200) // Cap at 200 events
+
+  events.value = newEvents
+}
+
+function connectRelay(relayState: RelayState) {
+  if (relayState.ws) return
+
+  try {
+    const ws = new WebSocket(relayState.url)
+    relayState.ws = ws
+
+    ws.onopen = () => {
+      relayState.connected = true
+      updateRelayStates()
+      isConnected.value = relays.some(r => r.connected)
+
+      // Subscribe to kind:1 (text notes) with limit 50
+      if (!subscriptionId) subscriptionId = generateSubId()
+      const req = JSON.stringify([
+        'REQ',
+        subscriptionId,
+        { kinds: [1], limit: 50 },
+      ])
+      ws.send(req)
+    }
+
+    ws.onmessage = (msg) => {
+      try {
+        const data = JSON.parse(msg.data)
+        const evt = parseEvent(data)
+        if (evt) addEvent(evt)
+      } catch {
+        // Skip malformed messages
+      }
+    }
+
+    ws.onclose = () => {
+      relayState.connected = false
+      relayState.ws = null
+      updateRelayStates()
+      isConnected.value = relays.some(r => r.connected)
+    }
+
+    ws.onerror = () => {
+      // Will trigger onclose
+    }
+  } catch {
+    relayState.connected = false
+    updateRelayStates()
+  }
+}
+
+function updateRelayStates() {
+  relayStates.value = relays.map(r => ({
+    url: r.url,
+    connected: r.connected,
+  }))
+}
+
+function connect() {
+  if (initialized) return
+  initialized = true
+
+  relays = RELAYS.map(url => ({ url, ws: null, connected: false }))
+  updateRelayStates()
+  relays.forEach(r => connectRelay(r))
+}
+
+function disconnect() {
+  if (subscriptionId) {
+    relays.forEach(r => {
+      if (r.ws && r.connected) {
+        try {
+          r.ws.send(JSON.stringify(['CLOSE', subscriptionId]))
+        } catch { /* ignore */ }
+      }
+    })
+    subscriptionId = null
+  }
+
+  relays.forEach(r => {
+    if (r.ws) {
+      r.ws.close()
+      r.ws = null
+      r.connected = false
+    }
+  })
+
+  updateRelayStates()
+  isConnected.value = false
+  initialized = false
+}
+
+export function useNostr() {
+  onUnmounted(() => {
+    // Clean up on component unmount
+    disconnect()
+  })
+
+  return {
+    events,
+    isConnected,
+    relayStates,
+    connect,
+    disconnect,
+  }
+}