新增: 相册展示模块（左侧幻灯片+进度条+目录选择）

- 左侧固定卡片展示照片幻灯片，淡入淡出切换
- 进度条动画显示当前照片剩余时间
- 设置窗口支持选择图片目录和切换间隔(5/10/15/20/30/60秒)
- Win32 SHBrowseForFolderW 目录选择对话框
- Go 端管理幻灯片状态，按间隔推送照片 data URI

photo.go

@@ -0,0 +1,166 @@
+package main
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	photoMu    sync.Mutex
+	photoFiles []string
+	photoIdx   int
+	photoDir   string
+	photoStop  chan struct{}
+	photoDone  chan struct{}
+)
+
+func scanPhotoDir(dir string) []string {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil
+	}
+	var files []string
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		ext := strings.ToLower(filepath.Ext(e.Name()))
+		switch ext {
+		case ".jpg", ".jpeg", ".png", ".bmp", ".webp", ".gif":
+			files = append(files, e.Name())
+		}
+	}
+	sort.Strings(files)
+	return files
+}
+
+func photoToDataURI(dir, name string) string {
+	path := filepath.Join(dir, name)
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return ""
+	}
+	ext := strings.ToLower(filepath.Ext(name))
+	mime := "image/jpeg"
+	switch ext {
+	case ".png":
+		mime = "image/png"
+	case ".gif":
+		mime = "image/gif"
+	case ".webp":
+		mime = "image/webp"
+	case ".bmp":
+		mime = "image/bmp"
+	}
+	return fmt.Sprintf("data:%s;base64,%s", mime, base64.StdEncoding.EncodeToString(data))
+}
+
+func pushCurrentPhoto(interval int) {
+	photoMu.Lock()
+	files := photoFiles
+	idx := photoIdx
+	dir := photoDir
+	photoMu.Unlock()
+
+	if len(files) == 0 || dir == "" {
+		evalJS(`if(window.updatePhotoFromGo) updatePhotoFromGo(null)`)
+		return
+	}
+	if idx >= len(files) {
+		idx = 0
+	}
+
+	src := photoToDataURI(dir, files[idx])
+	if src == "" {
+		return
+	}
+
+	data, _ := json.Marshal(map[string]interface{}{
+		"src":      src,
+		"counter":  fmt.Sprintf("%d / %d", idx+1, len(files)),
+		"interval": interval,
+	})
+	evalJS(fmt.Sprintf(`if(window.updatePhotoFromGo) updatePhotoFromGo(%s)`, string(data)))
+}
+
+func startPhotoLoop() {
+	cfg := loadConfig()
+	if cfg.PhotoDir == "" {
+		return
+	}
+
+	interval := cfg.PhotoInterval
+	if interval <= 0 {
+		interval = 15
+	}
+
+	files := scanPhotoDir(cfg.PhotoDir)
+	if len(files) == 0 {
+		log.Println("相册: 目录为空或无图片")
+		return
+	}
+
+	photoMu.Lock()
+	photoDir = cfg.PhotoDir
+	photoFiles = files
+	photoIdx = 0
+	stop := make(chan struct{})
+	done := make(chan struct{})
+	photoStop = stop
+	photoDone = done
+	photoMu.Unlock()
+
+	log.Printf("相册: 共 %d 张, 间隔 %ds", len(files), interval)
+	pushCurrentPhoto(interval)
+
+	go func() {
+		ticker := time.NewTicker(time.Duration(interval) * time.Second)
+		defer func() {
+			ticker.Stop()
+			close(done)
+		}()
+		for {
+			select {
+			case <-ticker.C:
+				photoMu.Lock()
+				if len(photoFiles) > 0 {
+					photoIdx = (photoIdx + 1) % len(photoFiles)
+				}
+				photoMu.Unlock()
+				pushCurrentPhoto(interval)
+			case <-stop:
+				return
+			}
+		}
+	}()
+}
+
+func stopPhotoLoop() {
+	photoMu.Lock()
+	stop := photoStop
+	done := photoDone
+	photoStop = nil
+	photoDone = nil
+	photoMu.Unlock()
+
+	if stop != nil {
+		close(stop)
+	}
+	if done != nil {
+		<-done
+	}
+}
+
+func restartPhotoLoop() {
+	stopPhotoLoop()
+	evalJS(`if(window.updatePhotoFromGo) updatePhotoFromGo(null)`)
+	startPhotoLoop()
+}