feat: implement notification center in frontend shell header

frontend/src/layouts/Shell.tsx

@@ -65,7 +65,10 @@ function CartDropdownContent() {
 export function Shell({ children }: { children: React.ReactNode }) {
   const { user, logout } = useAuth()
   const [isProfileOpen, setIsProfileOpen] = useState(false)
+  const [isNotificationsOpen, setIsNotificationsOpen] = useState(false)
+  const [notifications, setNotifications] = useState<any[]>([])
   const profileMenuRef = useRef<HTMLDivElement | null>(null)
+  const notificationsRef = useRef<HTMLDivElement | null>(null)
   const { totalItems: cartCount } = useCartStore(selectCartSummary)
 
   const isOwner = user?.role === 'owner'
@@ -78,13 +81,27 @@ export function Shell({ children }: { children: React.ReactNode }) {
       if (profileMenuRef.current && !profileMenuRef.current.contains(event.target as Node)) {
         setIsProfileOpen(false)
       }
+      if (notificationsRef.current && !notificationsRef.current.contains(event.target as Node)) {
+        setIsNotificationsOpen(false)
+      }
     }
 
     document.addEventListener('mousedown', handleClickOutside)
+    
+    // Simulate loading notifications (In prod, fetch from /api/v1/notifications)
+    if (user) {
+      setNotifications([
+        { id: 1, title: 'Bem-vindo!', message: 'Explore o marketplace SaveInMed.', date: new Date().toISOString(), read: false },
+        { id: 2, title: 'Perfil Completo', message: 'Seu cadastro foi verificado com sucesso.', date: new Date().toISOString(), read: true }
+      ])
+    }
+
     return () => {
       document.removeEventListener('mousedown', handleClickOutside)
     }
-  }, [])
+  }, [user])
+
+  const unreadCount = notifications.filter(n => !n.read).length
 
   return (
     <div className="min-h-screen bg-gray-100">
@@ -112,6 +129,47 @@ export function Shell({ children }: { children: React.ReactNode }) {
                   <a href="/shipping-settings" className="hover:underline whitespace-nowrap">Config. Entrega</a>
                 </>
               )}
+
+              {/* Notifications */}
+              <div className="relative" ref={notificationsRef}>
+                <button
+                  onClick={() => setIsNotificationsOpen(!isNotificationsOpen)}
+                  className="relative hover:bg-white/10 p-2 rounded-lg transition-colors block"
+                  title="Notificações"
+                >
+                  <svg className="h-6 w-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 17h5l-1.405-1.405A2.032 2.032 0 0118 14.158V11a6.002 6.002 0 00-4-5.659V5a2 2 0 10-4 0v.341C7.67 6.165 6 8.388 6 11v3.159c0 .538-.214 1.055-.595 1.436L4 17h5m6 0v1a3 3 0 11-6 0v-1m6 0H9" />
+                  </svg>
+                  {unreadCount > 0 && (
+                    <span className="absolute top-1 right-1 flex h-4 w-4 items-center justify-center rounded-full bg-orange-500 text-[10px] font-bold">
+                      {unreadCount}
+                    </span>
+                  )}
+                </button>
+
+                {isNotificationsOpen && (
+                  <div className="absolute right-0 mt-2 w-80 rounded-lg bg-white shadow-xl border border-gray-100 z-[100] text-gray-800">
+                    <div className="p-4 border-b flex justify-between items-center">
+                      <h3 className="font-bold text-sm">Notificações</h3>
+                      <button onClick={() => setNotifications([])} className="text-xs text-blue-600 hover:underline">Limpar tudo</button>
+                    </div>
+                    <div className="max-h-64 overflow-y-auto">
+                      {notifications.length === 0 ? (
+                        <div className="p-8 text-center text-gray-400 text-sm italic">Nenhuma notificação</div>
+                      ) : (
+                        notifications.map(n => (
+                          <div key={n.id} className={`p-4 border-b hover:bg-gray-50 transition-colors ${!n.read ? 'bg-blue-50/30' : ''}`}>
+                            <p className="font-semibold text-xs">{n.title}</p>
+                            <p className="text-xs text-gray-600 mt-1">{n.message}</p>
+                            <p className="text-[10px] text-gray-400 mt-2">{new Date(n.date).toLocaleDateString()}</p>
+                          </div>
+                        ))
+                      )}
+                    </div>
+                  </div>
+                )}
+              </div>
+
               <div className="relative group">
                 <a
                   href="/cart"