feat: notifikasi real-time bug baru via WebSocket

- presence.ts: tambah notifSubs (ADMIN+DEVELOPER) dan broadcastNotification
- app.ts: broadcast new_bug event setelah bug dibuat, update WS handler
- usePresence: terima callback onNewBug, expose NewBugPayload type
- DashboardLayout: pasang usePresence, tampilkan Mantine notification saat bug baru masuk

src/frontend/hooks/usePresence.ts

@@ -1,11 +1,22 @@
 import { useEffect, useRef, useState } from 'react'
 import { useSession } from './useAuth'
 
-export function usePresence() {
+export interface NewBugPayload {
+  id: string
+  description: string
+  appId: string | null
+  source: string
+  affectedVersion: string
+  createdAt: string
+}
+
+export function usePresence(onNewBug?: (bug: NewBugPayload) => void) {
   const { data } = useSession()
   const [onlineUserIds, setOnlineUserIds] = useState<string[]>([])
   const wsRef = useRef<WebSocket | null>(null)
   const reconnectTimer = useRef<ReturnType<typeof setTimeout> | undefined>(undefined)
+  const onNewBugRef = useRef(onNewBug)
+  onNewBugRef.current = onNewBug
 
   useEffect(() => {
     if (!data?.user) return
@@ -18,6 +29,7 @@ export function usePresence() {
       ws.onmessage = (e) => {
         const msg = JSON.parse(e.data)
         if (msg.type === 'presence') setOnlineUserIds(msg.online)
+        if (msg.type === 'new_bug') onNewBugRef.current?.(msg.bug)
       }
       ws.onclose = () => {
         wsRef.current = null