Fix findLatestScreenshot sorting by pre-fetching file info

The sort comparator was calling Info() and silently discarding errors,
which could cause nil dereferences or incorrect ordering. Pre-fetch
ModTime into a struct so the sort always has valid data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

main.go

@@ -30,17 +30,29 @@ func getDesktopPath() string {
 	return filepath.Join(home, "Desktop")
 }
 
+type screenshotFile struct {
+	path    string
+	modTime time.Time
+}
+
 func findLatestScreenshot(desktop string) (string, error) {
 	entries, err := os.ReadDir(desktop)
 	if err != nil {
 		return "", err
 	}
 
-	var screenshots []os.DirEntry
+	var screenshots []screenshotFile
 	for _, e := range entries {
 		name := e.Name()
 		if strings.HasPrefix(name, "Screenshot") && strings.HasSuffix(name, ".png") {
-			screenshots = append(screenshots, e)
+			info, err := e.Info()
+			if err != nil {
+				continue
+			}
+			screenshots = append(screenshots, screenshotFile{
+				path:    filepath.Join(desktop, name),
+				modTime: info.ModTime(),
+			})
 		}
 	}
 
@@ -50,12 +62,10 @@ func findLatestScreenshot(desktop string) (string, error) {
 
 	// Sort by modification time (newest first)
 	sort.Slice(screenshots, func(i, j int) bool {
-		infoI, _ := screenshots[i].Info()
-		infoJ, _ := screenshots[j].Info()
-		return infoI.ModTime().After(infoJ.ModTime())
+		return screenshots[i].modTime.After(screenshots[j].modTime)
 	})
 
-	return filepath.Join(desktop, screenshots[0].Name()), nil
+	return screenshots[0].path, nil
 }
 
 func serveAndDelete(w http.ResponseWriter, path string) {