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

settings.go

@@ -138,6 +138,8 @@ func openSettingsWindow() {
 				"imagePath":       cfg.ImagePath,
 				"showSeconds":     cfg.ShowSeconds,
 				"ainewsCard":      !cfg.HideAINews,
+				"photoDir":        cfg.PhotoDir,
+				"photoInterval":   cfg.PhotoInterval,
 			})
 			return string(data)
 		})
@@ -364,6 +366,40 @@ func openSettingsWindow() {
 			return ""
 		})
 
+		w.Bind("pickPhotoDir", func() string {
+			hwnd := uintptr(w.Window())
+			dir := browseForFolderDialog(hwnd)
+			if dir == "" {
+				return ""
+			}
+			cfg := loadConfig()
+			cfg.PhotoDir = dir
+			if cfg.PhotoInterval <= 0 {
+				cfg.PhotoInterval = 15
+			}
+			saveConfig(cfg)
+			restartPhotoLoop()
+			return dir
+		})
+
+		w.Bind("clearPhotoDir", func() string {
+			cfg := loadConfig()
+			cfg.PhotoDir = ""
+			saveConfig(cfg)
+			restartPhotoLoop()
+			return ""
+		})
+
+		w.Bind("savePhotoInterval", func(val int) string {
+			cfg := loadConfig()
+			cfg.PhotoInterval = val
+			saveConfig(cfg)
+			if cfg.PhotoDir != "" {
+				restartPhotoLoop()
+			}
+			return ""
+		})
+
 		w.SetHtml(settingsHTML)
 
 		hwnd := uintptr(w.Window())