fix: 保留用户/规则高级设置并增强节点运行时恢复 (#468)

* fix: 用户编辑时 maxConn 字段未正确回填

- User 接口添加 maxConn 类型定义
- handleEdit 中回填 maxConn 值
- normalizeUserItem 添加 maxConn 字段处理

解决编辑用户时最大连接数显示为 0 的问题

* fix: 保留转发设置并增强节点运行时恢复

go-gost/x/config/persist.go

@@ -0,0 +1,94 @@
+package config
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+var (
+	persistPath   string
+	persistMu     sync.Mutex
+	persistEnable bool
+)
+
+// SetPersistPath sets the file path where runtime config changes will be
+// automatically persisted. Call this once during agent startup before any
+// OnUpdate mutations occur.
+func SetPersistPath(path string) {
+	persistMu.Lock()
+	defer persistMu.Unlock()
+	persistPath = path
+}
+
+func PersistPath() string {
+	persistMu.Lock()
+	defer persistMu.Unlock()
+	return persistPath
+}
+
+// EnablePersist turns on automatic persistence. Call this after the initial
+// config has been loaded (e.g. after program.Start) so that startup loading
+// does not trigger redundant disk writes.
+func EnablePersist() {
+	persistMu.Lock()
+	defer persistMu.Unlock()
+	persistEnable = true
+}
+
+// persist writes the current global config to the configured file atomically.
+func persist() {
+	persistMu.Lock()
+	path := persistPath
+	enabled := persistEnable
+	persistMu.Unlock()
+
+	if !enabled || path == "" {
+		return
+	}
+
+	cfg := Global()
+	if cfg == nil {
+		return
+	}
+
+	var buf bytes.Buffer
+	enc := json.NewEncoder(&buf)
+	enc.SetIndent("", "  ")
+	if err := enc.Encode(cfg); err != nil {
+		fmt.Printf("⚠️ config persist: marshal failed: %v\n", err)
+		return
+	}
+
+	// Atomic write: write to temp file then rename
+	dir := filepath.Dir(path)
+	tmp, err := os.CreateTemp(dir, ".gost-*.tmp")
+	if err != nil {
+		fmt.Printf("⚠️ config persist: create temp file failed: %v\n", err)
+		return
+	}
+	tmpName := tmp.Name()
+
+	if _, err := tmp.Write(buf.Bytes()); err != nil {
+		tmp.Close()
+		os.Remove(tmpName)
+		fmt.Printf("⚠️ config persist: write failed: %v\n", err)
+		return
+	}
+	if err := tmp.Close(); err != nil {
+		os.Remove(tmpName)
+		fmt.Printf("⚠️ config persist: close temp file failed: %v\n", err)
+		return
+	}
+
+	if err := os.Rename(tmpName, path); err != nil {
+		os.Remove(tmpName)
+		fmt.Printf("⚠️ config persist: rename failed: %v\n", err)
+		return
+	}
+
+	fmt.Printf("💾 节点配置已持久化到 %s\n", path)
+}