fix: Phase 6联调 — 插件管理器端口修正 + 多模型配置系统整合 + 历史消息刷新修复

## 调试日志

### 1. 插件管理器启动失败
- **症状**: DevTools 显示插件管理器一直"已停止"，手动启动正常
- **排查**: 对比 process-manager.js 传入的环境变量 vs plugin-manager config.go 读取的变量
- **根因**: config.js 传入 PLUGIN_MANAGER_PORT=8094，但 config.go 读取 os.Getenv("PORT")，env 名不匹配。且 process.env 中 PORT 泄露时被误读为 9090，与 DevTools 端口冲突
- **修复**: config.js 将 PLUGIN_MANAGER_PORT → PORT，使 env 名与代码一致 (c3055f4)

### 2. 历史消息刷新后消失
- **症状**: 浏览器刷新后聊天历史清空
- **排查**: WebSocket history_response handler 中 if (msg.messages) 对空数组 [] 为 truthy
- **根因**: 后端返回空的 history_response (缓存为空) 时，空数组覆盖了 HTTP 已加载的消息
- **修复**: useWebSocket.ts 改为 if (msg.messages && msg.messages.length > 0)，空数组走 else-if 分支仅打日志，不覆盖已有消息

### 3. Phase 6 多模型配置系统
- Gateway: ModelsConfigStore (JSON文件持久化) + Admin CRUD API (providers/models/routing)
- ai-core: ModelSelector 支持按 purpose 选择 + fallback_chain，无配置时回退 .env
- DevTools: 模型配置管理面板 (Providers/Models/Routing 三Tab)、在线模型查询代理、路由表单 checkbox 多选、关键词搜索过滤
- .gitignore: models.json + platform_configs.json

### 4. 多端客户端追踪
- Hub 新增 knownClients 映射 (clientID → KnownClient)，在线/离线状态追踪
- 客户端备注持久化到 PostgreSQL
- DevTools 客户端管理面板

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/gateway/internal/ws/hub.go

@@ -39,10 +39,23 @@ type Message struct {
 	MsgType     string               `json:"msg_type,omitempty"`
 	Attachments []MessageAttachment  `json:"attachments,omitempty"`
 	Timestamp   int64                `json:"timestamp"`
+	ClientInfo  *ClientInfo          `json:"client_info,omitempty"`
 }
 
 const maxRecentMessages = 20
 
+// KnownClient tracks a device that has ever connected (online or offline).
+type KnownClient struct {
+	ClientID    string    `json:"client_id"`
+	UserID      string    `json:"user_id"`
+	DeviceName  string    `json:"device_name"`
+	UserAgent   string    `json:"user_agent"`
+	Note        string    `json:"note"`         // user-assigned label
+	Online      bool      `json:"online"`
+	LastSeenAt  time.Time `json:"last_seen_at"`
+	FirstSeenAt time.Time `json:"first_seen_at"`
+}
+
 // Hub WebSocket连接池
 type Hub struct {
 	mu         sync.RWMutex
@@ -76,6 +89,9 @@ type Hub struct {
 	pendingProactive map[string][]json.RawMessage // userID -> queued messages
 	aiCoreURL       string
 	internalToken   string
+
+	// 多端客户端追踪: clientID -> KnownClient (在线+离线)
+	knownClients map[string]*KnownClient
 }
 
 // SetStore 设置持久化存储 (可选)
@@ -100,6 +116,7 @@ func NewHub() *Hub {
 		iotStopCh:   make(chan struct{}),
 		idleTimeout: 30 * time.Minute, // 默认30分钟
 		pendingProactive: make(map[string][]json.RawMessage),
+		knownClients:     make(map[string]*KnownClient),
 	}
 }
 
@@ -254,6 +271,34 @@ func (h *Hub) Run() {
 					MessageCount: 0,
 				}
 			}
+
+			// 多端客户端追踪
+			if client.ClientID != "" {
+				now := time.Now()
+				if kc, ok := h.knownClients[client.ClientID]; ok {
+					kc.Online = true
+					kc.LastSeenAt = now
+					kc.DeviceName = client.DeviceName
+					kc.UserAgent = client.UserAgent
+				} else {
+					h.knownClients[client.ClientID] = &KnownClient{
+						ClientID:    client.ClientID,
+						UserID:      client.UserID,
+						DeviceName:  client.DeviceName,
+						UserAgent:   client.UserAgent,
+						Online:      true,
+						LastSeenAt:  now,
+						FirstSeenAt: now,
+					}
+				}
+			}
+
+			// 持久化客户端记录到数据库
+			if client.ClientID != "" && h.store != nil && h.store.IsAvailable() {
+				if err := h.store.UpsertClient(client.ClientID, client.UserID, client.DeviceName, client.UserAgent); err != nil {
+					logger.Printf("[WS] 持久化客户端记录失败: %v", err)
+				}
+			}
 			// Phase 2: 检测是否为重连 (之前处于离线状态)
 		wasOffline := len(h.userClients[client.UserID]) == 1 // 刚加入，之前为0
 		h.mu.Unlock()
@@ -308,6 +353,23 @@ func (h *Hub) Run() {
 						s.State = "idle"
 					}
 				}
+
+				// 多端客户端追踪: 检查同一 clientID 是否还有其他连接
+				if client.ClientID != "" {
+					hasOtherClientConn := false
+					for c := range h.clients {
+						if c.ClientID == client.ClientID {
+							hasOtherClientConn = true
+							break
+						}
+					}
+					if !hasOtherClientConn {
+						if kc, ok := h.knownClients[client.ClientID]; ok {
+							kc.Online = false
+							kc.LastSeenAt = time.Now()
+						}
+					}
+				}
 			}
 			h.mu.Unlock()
 
@@ -362,6 +424,23 @@ func (h *Hub) Run() {
 							s.State = "idle"
 						}
 					}
+
+					// 多端客户端追踪
+					if client.ClientID != "" {
+						hasOtherClientConn := false
+						for c := range h.clients {
+							if c.ClientID == client.ClientID {
+								hasOtherClientConn = true
+								break
+							}
+						}
+						if !hasOtherClientConn {
+							if kc, ok := h.knownClients[client.ClientID]; ok {
+								kc.Online = false
+								kc.LastSeenAt = time.Now()
+							}
+						}
+					}
 				}
 				h.mu.Unlock()
 
@@ -766,3 +845,62 @@ func (h *Hub) DeleteConversation(userID, sessionID string) {
 	key := cacheKey(userID, sessionID)
 	h.conversationCache.Delete(key)
 }
+
+// ========== 多端客户端追踪 ==========
+
+// GetKnownClients returns all known clients (online + offline).
+func (h *Hub) GetKnownClients(userID string) []KnownClient {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	result := make([]KnownClient, 0)
+	for _, kc := range h.knownClients {
+		if userID == "" || kc.UserID == userID {
+			cp := *kc
+			cp.UserAgent = "" // don't leak UA in list
+			result = append(result, cp)
+		}
+	}
+	return result
+}
+
+// UpdateClientNote sets a user-defined note/label on a client.
+func (h *Hub) UpdateClientNote(clientID, note string) bool {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	kc, ok := h.knownClients[clientID]
+	if !ok {
+		return false
+	}
+	kc.Note = note
+	return true
+}
+
+// ClientInfo returns the ClientInfo for a given client.
+func (h *Hub) ClientInfo(clientID string) *ClientInfo {
+	h.mu.RLock()
+	defer h.mu.RUnlock()
+
+	kc, ok := h.knownClients[clientID]
+	if !ok {
+		return nil
+	}
+	return &ClientInfo{
+		ClientID:   kc.ClientID,
+		DeviceName: kc.DeviceName,
+		UserAgent:  kc.UserAgent,
+	}
+}
+
+// buildClientInfo builds a ClientInfo from a Client.
+func buildClientInfo(c *Client) *ClientInfo {
+	if c.ClientID == "" {
+		return nil
+	}
+	return &ClientInfo{
+		ClientID:   c.ClientID,
+		DeviceName: c.DeviceName,
+		UserAgent:  c.UserAgent,
+	}
+}