feat(logging): 增加 Seq 日志集成与标准输出重定向

- 新增 SeqWriter 支持，将日志异步推送到 Seq 平台，支持多进程实例区分
- 实现 redirectStdout 函数，重定向 os.Stdout 和标准 log 包输出，确保 fmt.Println 等输出被捕获并记录
- 更新 README 文档，增加 Seq 日志集成的说明与配置链接
- 扩展 Logger 结构，支持动态添加输出目标，提升日志记录灵活性

log/logger.go

@@ -2,13 +2,17 @@ package log
 
 import (
 	"bufio"
+	"bytes"
+	"encoding/json"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/rs/zerolog"
@@ -25,6 +29,7 @@ type ErrorRecord struct {
 // Logger 日志核心结构体，封装 zerolog
 type Logger struct {
 	zl        zerolog.Logger
+	mw        *multiWriter // 动态多输出，支持运行时追加 SeqWriter 等
 	logLevel  int
 	errors    []ErrorRecord
 	errIdx    int // 环形缓冲写入位置
@@ -69,8 +74,8 @@ func NewLogger(logLevel int, logFile string, maxErrors int) *Logger {
 		writers = append(writers, fw)
 	}
 
-	multi := zerolog.MultiLevelWriter(writers...)
-	zl := zerolog.New(multi).
+	mw := &multiWriter{writers: writers}
+	zl := zerolog.New(mw).
 		Level(level).
 		With().
 		Timestamp().
@@ -79,6 +84,7 @@ func NewLogger(logLevel int, logFile string, maxErrors int) *Logger {
 
 	l := &Logger{
 		zl:        zl,
+		mw:        mw,
 		logLevel:  logLevel,
 		maxErrors: maxErrors,
 	}
@@ -116,8 +122,8 @@ func NewLoggerNoCaller(logLevel int, logFile string, maxErrors int) *Logger {
 		writers = append(writers, fw)
 	}
 
-	multi := zerolog.MultiLevelWriter(writers...)
-	zl := zerolog.New(multi).
+	mw := &multiWriter{writers: writers}
+	zl := zerolog.New(mw).
 		Level(level).
 		With().
 		Timestamp().
@@ -125,6 +131,7 @@ func NewLoggerNoCaller(logLevel int, logFile string, maxErrors int) *Logger {
 
 	l := &Logger{
 		zl:        zl,
+		mw:        mw,
 		logLevel:  logLevel,
 		maxErrors: maxErrors,
 	}
@@ -145,6 +152,7 @@ func NewTestLogger() *Logger {
 func (l *Logger) SetOutput(w io.Writer) {
 	if w == io.Discard {
 		l.zl = zerolog.New(w).Level(zerolog.Disabled)
+		l.mw = nil
 		return
 	}
 	consoleWriter := zerolog.ConsoleWriter{
@@ -159,7 +167,9 @@ func (l *Logger) SetOutput(w io.Writer) {
 			return fmt.Sprintf("[%s]", i)
 		},
 	}
-	l.zl = zerolog.New(consoleWriter).
+	mw := &multiWriter{writers: []io.Writer{consoleWriter}}
+	l.mw = mw
+	l.zl = zerolog.New(mw).
 		With().
 		Timestamp().
 		Caller().
@@ -422,6 +432,205 @@ func shortenPath(file string) string {
 	return file
 }
 
+// --- multiWriter: 支持运行时追加输出目标 ---
+
+// multiWriter 实现 zerolog.LevelWriter，允许在 Logger 创建后动态追加新的输出（如 SeqWriter）
+type multiWriter struct {
+	mu      sync.RWMutex
+	writers []io.Writer
+}
+
+func (mw *multiWriter) Write(p []byte) (int, error) {
+	mw.mu.RLock()
+	defer mw.mu.RUnlock()
+	for _, w := range mw.writers {
+		_, _ = w.Write(p)
+	}
+	return len(p), nil
+}
+
+// WriteLevel 实现 zerolog.LevelWriter，使 zerolog 的级别过滤正确传递给各子 Writer
+func (mw *multiWriter) WriteLevel(l zerolog.Level, p []byte) (int, error) {
+	mw.mu.RLock()
+	defer mw.mu.RUnlock()
+	for _, w := range mw.writers {
+		if lw, ok := w.(zerolog.LevelWriter); ok {
+			_, _ = lw.WriteLevel(l, p)
+		} else {
+			_, _ = w.Write(p)
+		}
+	}
+	return len(p), nil
+}
+
+func (mw *multiWriter) add(w io.Writer) {
+	mw.mu.Lock()
+	mw.writers = append(mw.writers, w)
+	mw.mu.Unlock()
+}
+
+// --- SeqWriter: 异步推送到 Seq（CLEF 格式）---
+
+// SeqWriter 将 zerolog JSON 日志通过 channel 队列异步发送到 Seq。
+// Write() 仅做 channel <- bytes，O(1) 非阻塞，绝不阻塞 web 请求处理 goroutine。
+// channel 容量 10000，满时丢弃新条目（dropped 计数），不会影响主服务。
+type SeqWriter struct {
+	seqUrl   string
+	apiKey   string
+	instance string
+	queue    chan []byte
+	dropped  int64
+	client   *http.Client
+}
+
+func newSeqWriter(seqUrl, apiKey, instance string) *SeqWriter {
+	w := &SeqWriter{
+		seqUrl:   strings.TrimRight(seqUrl, "/"),
+		apiKey:   apiKey,
+		instance: instance,
+		queue:    make(chan []byte, 10000),
+		client:   &http.Client{Timeout: 5 * time.Second},
+	}
+	go w.run()
+	return w
+}
+
+// Write 将字节塞入 channel 即返回，由后台 goroutine 消费发送
+func (w *SeqWriter) Write(p []byte) (int, error) {
+	clef := w.toClef(p)
+	select {
+	case w.queue <- clef:
+	default:
+		atomic.AddInt64(&w.dropped, 1)
+	}
+	return len(p), nil
+}
+
+// toClef 将 zerolog JSON 字段映射到 Seq CLEF 格式
+// zerolog: time/level/message(msg) → CLEF: @t/@l/@mt
+func (w *SeqWriter) toClef(p []byte) []byte {
+	trimmed := bytes.TrimSpace(p)
+	var m map[string]interface{}
+	if err := json.Unmarshal(trimmed, &m); err != nil {
+		// 非 JSON（如 fmt.Println 直接输出），包装为纯文本日志
+		return []byte(fmt.Sprintf(`{"@t":%q,"@l":"Information","@mt":%q,"source":"stdout","instance":%q}`,
+			time.Now().Format(time.RFC3339), strings.TrimSpace(string(p)), w.instance))
+	}
+
+	clef := make(map[string]interface{}, len(m)+3)
+	for k, v := range m {
+		clef[k] = v
+	}
+
+	// time → @t（zerolog 格式 "2006-01-02 15:04:05" → ISO 8601）
+	if t, ok := m["time"].(string); ok {
+		delete(clef, "time")
+		if pt, err := time.ParseInLocation("2006-01-02 15:04:05", t, time.Local); err == nil {
+			clef["@t"] = pt.Format(time.RFC3339)
+		} else {
+			clef["@t"] = t
+		}
+	} else {
+		clef["@t"] = time.Now().Format(time.RFC3339)
+	}
+
+	// level → @l
+	if lv, ok := m["level"].(string); ok {
+		delete(clef, "level")
+		switch lv {
+		case "debug":
+			clef["@l"] = "Debug"
+		case "info":
+			clef["@l"] = "Information"
+		case "warn":
+			clef["@l"] = "Warning"
+		case "error":
+			clef["@l"] = "Error"
+		case "fatal":
+			clef["@l"] = "Fatal"
+		default:
+			clef["@l"] = lv
+		}
+	}
+
+	// message/msg → @mt
+	if msg, ok := m["message"].(string); ok {
+		delete(clef, "message")
+		clef["@mt"] = msg
+	} else if msg, ok := m["msg"].(string); ok {
+		delete(clef, "msg")
+		clef["@mt"] = msg
+	}
+
+	if w.instance != "" {
+		clef["instance"] = w.instance
+	}
+
+	b, _ := json.Marshal(clef)
+	return b
+}
+
+// run 后台 goroutine：每 100 条或 500ms 批量 POST 到 Seq
+func (w *SeqWriter) run() {
+	batch := make([][]byte, 0, 100)
+	ticker := time.NewTicker(500 * time.Millisecond)
+	defer ticker.Stop()
+	for {
+		select {
+		case entry := <-w.queue:
+			batch = append(batch, entry)
+			if len(batch) >= 100 {
+				w.flush(batch)
+				batch = batch[:0]
+			}
+		case <-ticker.C:
+			if len(batch) > 0 {
+				w.flush(batch)
+				batch = batch[:0]
+			}
+		}
+	}
+}
+
+func (w *SeqWriter) flush(batch [][]byte) {
+	var buf bytes.Buffer
+	for _, entry := range batch {
+		buf.Write(entry)
+		buf.WriteByte('\n')
+	}
+	req, err := http.NewRequest("POST", w.seqUrl+"/api/events/raw?clef", &buf)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "[seq] build request error: %v\n", err)
+		return
+	}
+	req.Header.Set("Content-Type", "application/vnd.serilog.clef")
+	if w.apiKey != "" {
+		req.Header.Set("X-Seq-ApiKey", w.apiKey)
+	}
+	resp, err := w.client.Do(req)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "[seq] send error: %v (dropped=%d)\n", err, atomic.LoadInt64(&w.dropped))
+		return
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 400 {
+		body, _ := io.ReadAll(resp.Body)
+		fmt.Fprintf(os.Stderr, "[seq] server returned %d: %s\n", resp.StatusCode, string(body))
+	}
+}
+
+// SetSeqWriter 将 Seq HTTP 推送器附加到当前 Logger（不影响已有的控制台/文件输出）
+// seqUrl: Seq 服务地址，如 "http://127.0.0.1:5341"
+// apiKey: Seq API Key，免费单用户版留空
+// instance: 实例标识，建议用 config 的 port 字段区分同机多进程，如 "8085"
+func (l *Logger) SetSeqWriter(seqUrl, apiKey, instance string) {
+	if seqUrl == "" || l.mw == nil {
+		return
+	}
+	sw := newSeqWriter(seqUrl, apiKey, instance)
+	l.mw.add(sw)
+}
+
 // isInfrastructureFile 判断文件是否为基础设施（日志/DB/缓存/通用工具）管线，
 // 这些文件在调用栈中会被跳过，以显示真正的业务调用者。
 // context.go 是 Display/View 的纯中间层，也作为基础设施跳过。