补全 P0：筛选、访客图片与双向输入状态

- 工作台会话列表支持状态/紧急筛选
- 访客 Widget 支持 jpg/png/gif 图片预览发送
- WebSocket 支持访客输入中通知客服，客服输入中通知访客
- 工作台聊天区展示「访客正在输入」动画

server/internal/ws/ws.go

@@ -135,21 +135,62 @@ func (h *Hub) BroadcastToVisitor(tenantID, sessionID uint, message []byte) {
 	}
 }
 
+// BroadcastToSessionStaff 仅推送给可查看该会话的工作人员（不含访客）。
+func (h *Hub) BroadcastToSessionStaff(tenantID uint, agentID *uint, message []byte) {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	for client := range h.clients {
+		if client.TenantID != tenantID || client.Kind != "agent" {
+			continue
+		}
+		if client.Role == "admin" || client.Role == "supervisor" ||
+			(agentID != nil && client.Role == "agent" && client.UserID == *agentID) {
+			h.send(client, message)
+		}
+	}
+}
+
 func handleClientEvent(client *Client, event ClientEvent) {
-	if client.Kind != "agent" || event.Type != "typing" || event.SessionID == 0 {
+	if event.Type != "typing" || event.SessionID == 0 {
 		return
 	}
 	var session model.Session
 	if err := model.DB.Where("id = ? AND tenant_id = ?", event.SessionID, client.TenantID).First(&session).Error; err != nil {
 		return
 	}
+
+	// 访客输入中 → 通知可接待的客服
+	if client.Kind == "visitor" {
+		if client.SessionID == nil || *client.SessionID != event.SessionID {
+			return
+		}
+		if session.Status == "ended" || session.Status == "archived" {
+			return
+		}
+		payload, err := NewEvent("typing", session.ID, map[string]string{"from": "visitor"})
+		if err != nil {
+			return
+		}
+		if session.AgentID == nil {
+			DefaultHub.BroadcastToTenantStaff(session.TenantID, payload)
+			return
+		}
+		DefaultHub.BroadcastToSessionStaff(session.TenantID, session.AgentID, payload)
+		return
+	}
+
+	// 客服输入中 → 通知访客
+	if client.Kind != "agent" {
+		return
+	}
 	if client.Role == "agent" && (session.AgentID == nil || *session.AgentID != client.UserID) {
 		return
 	}
 	if client.Role != "agent" && client.Role != "admin" && client.Role != "supervisor" {
 		return
 	}
-	payload, err := NewEvent("typing", session.ID, nil)
+	payload, err := NewEvent("typing", session.ID, map[string]string{"from": "agent"})
 	if err == nil {
 		DefaultHub.BroadcastToVisitor(session.TenantID, session.ID, payload)
 	}