webui4frpc: 独立可用的可视化 frpc 控制器 (M0)

- 零 frp 源码依赖，单二进制 (Go + Vue3 + VueFlow + Element Plus)
- 画布多对多连线，渲染 tcp/udp/http/https frpc 配置
- worker 进程管理：自愈、日志轮转、崩溃退避重启
- frpc 一键安装 (GitHub Releases) + 手动指定路径
- 三页 UI：状态(默认)/连接配置/设置
- 状态页实时节点/转发状态，节点可增删改启停
- 画布冲突检查：端口/域名冲突标红 + 弹窗拦截保存
- backend 单测覆盖 store/render/process/httpapi/install
- plan.md + FRPC_FEATURES_AUDIT.md 文档

internal/process/rotating.go

@@ -0,0 +1,73 @@
+package process
+
+import (
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// rotatingFile appends to a log file and rotates it once it exceeds maxSize.
+type rotatingFile struct {
+	mu      sync.Mutex
+	path    string
+	maxSize int64
+	f       *os.File
+	size    int64
+}
+
+func newRotatingFile(path string, maxSize int64) (*rotatingFile, error) {
+	if maxSize <= 0 {
+		maxSize = 10 * 1024 * 1024
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return nil, err
+	}
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0o644)
+	if err != nil {
+		return nil, err
+	}
+	info, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, err
+	}
+	return &rotatingFile{path: path, maxSize: maxSize, f: f, size: info.Size()}, nil
+}
+
+func (r *rotatingFile) Write(p []byte) (int, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if r.f == nil {
+		f, err := os.OpenFile(r.path, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0o644)
+		if err != nil {
+			return 0, err
+		}
+		r.f = f
+	}
+	if r.size > 0 && r.size+int64(len(p)) > r.maxSize {
+		_ = r.f.Close()
+		_ = os.Rename(r.path, r.path+".1")
+		f, err := os.OpenFile(r.path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o644)
+		if err != nil {
+			r.f = nil
+			return 0, err
+		}
+		r.f = f
+		r.size = 0
+	}
+	n, err := r.f.Write(p)
+	r.size += int64(n)
+	return n, err
+}
+
+func (r *rotatingFile) Close() error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	if r.f != nil {
+		err := r.f.Close()
+		r.f = nil
+		return err
+	}
+	return nil
+}