add WebSocket support for real-time delivery updates with JWT authentication and automatic reconnection

backend/internal/ws/hub.go

@@ -0,0 +1,48 @@
+package ws
+
+import "sync"
+
+type Hub struct {
+	mu      sync.RWMutex
+	clients map[*Client]struct{}
+}
+
+func NewHub() *Hub {
+	return &Hub{
+		clients: make(map[*Client]struct{}),
+	}
+}
+
+func (h *Hub) Register(c *Client) {
+	h.mu.Lock()
+	h.clients[c] = struct{}{}
+	h.mu.Unlock()
+}
+
+func (h *Hub) Unregister(c *Client) {
+	h.mu.Lock()
+	if _, ok := h.clients[c]; ok {
+		delete(h.clients, c)
+		close(c.send)
+	}
+	h.mu.Unlock()
+}
+
+func (h *Hub) Broadcast(msg []byte) {
+	if msg == nil {
+		return
+	}
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+	for c := range h.clients {
+		select {
+		case c.send <- msg:
+		default:
+			// Client too slow, schedule disconnect
+			go func(c *Client) {
+				h.Unregister(c)
+				c.conn.Close()
+			}(c)
+		}
+	}
+}