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/platform-bridge/internal/logging/logger.go

@@ -0,0 +1,149 @@
+package logging
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
+
+// LogEntry represents one message log record.
+type LogEntry struct {
+	Timestamp   time.Time `json:"timestamp"`
+	Direction   string    `json:"direction"` // "incoming" or "outgoing"
+	Platform    string    `json:"platform"`
+	ChannelID   string    `json:"channel_id"`
+	SenderID    string    `json:"sender_id"`
+	SenderName  string    `json:"sender_name"`
+	Content     string    `json:"content"`
+	ContentType string    `json:"content_type"`
+	MessageID   string    `json:"message_id,omitempty"`
+	Success     bool      `json:"success"`
+	Error       string    `json:"error,omitempty"`
+}
+
+// Logger writes message logs to per-platform JSONL files.
+type Logger struct {
+	mu    sync.Mutex
+	dir   string
+	files map[string]*os.File
+}
+
+// NewLogger creates a Logger, ensuring the log directory exists.
+func NewLogger(dir string) (*Logger, error) {
+	if err := os.MkdirAll(dir, 0750); err != nil {
+		return nil, fmt.Errorf("create log dir: %w", err)
+	}
+	return &Logger{
+		dir:   dir,
+		files: make(map[string]*os.File),
+	}, nil
+}
+
+// Log writes a log entry to the appropriate platform log file.
+func (l *Logger) Log(entry LogEntry) error {
+	if entry.Timestamp.IsZero() {
+		entry.Timestamp = time.Now()
+	}
+
+	f, err := l.getOrCreateFile(entry.Platform)
+	if err != nil {
+		return err
+	}
+
+	data, err := json.Marshal(entry)
+	if err != nil {
+		return fmt.Errorf("marshal log entry: %w", err)
+	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	if _, err := f.Write(append(data, '\n')); err != nil {
+		return fmt.Errorf("write log: %w", err)
+	}
+	return f.Sync()
+}
+
+// ReadLogs reads the last N log entries for a platform, newest first.
+func (l *Logger) ReadLogs(platform string, limit int) ([]LogEntry, error) {
+	if limit <= 0 || limit > 1000 {
+		limit = 1000
+	}
+
+	l.mu.Lock()
+	// Flush any pending writes to the file before reading.
+	if f, ok := l.files[platform]; ok {
+		f.Sync()
+	}
+	l.mu.Unlock()
+
+	path := filepath.Join(l.dir, platform+".log")
+	f, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return []LogEntry{}, nil
+		}
+		return nil, fmt.Errorf("open log file: %w", err)
+	}
+	defer f.Close()
+
+	// Read all lines, keep only the last `limit`.
+	var lines []string
+	scanner := bufio.NewScanner(f)
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+	for scanner.Scan() {
+		lines = append(lines, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("read log file: %w", err)
+	}
+
+	// Take last N lines and reverse.
+	start := len(lines) - limit
+	if start < 0 {
+		start = 0
+	}
+	lines = lines[start:]
+
+	entries := make([]LogEntry, 0, len(lines))
+	for i := len(lines) - 1; i >= 0; i-- {
+		var entry LogEntry
+		if err := json.Unmarshal([]byte(lines[i]), &entry); err != nil {
+			continue // Skip corrupted lines.
+		}
+		entries = append(entries, entry)
+	}
+	return entries, nil
+}
+
+// Close closes all open log file handles.
+func (l *Logger) Close() error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	for _, f := range l.files {
+		f.Close()
+	}
+	l.files = make(map[string]*os.File)
+	return nil
+}
+
+func (l *Logger) getOrCreateFile(platform string) (*os.File, error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	if f, ok := l.files[platform]; ok {
+		return f, nil
+	}
+
+	path := filepath.Join(l.dir, platform+".log")
+	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0640)
+	if err != nil {
+		return nil, fmt.Errorf("open log file %s: %w", path, err)
+	}
+	l.files[platform] = f
+	return f, nil
+}