refactor: 调整 LastDiffToImage 函数中的背景图大小和位置，增加边距以改善图像布局效果

service/beatleader/model.go

@@ -622,13 +622,13 @@ func (p PlayerDataLite) LastDiffToImage(lastDayQueryData PlayerDataLite) string
 	totalWidth := maxX - minX
 	totalHeight := maxY - minY
 
-	background := image.NewRGBA(image.Rect(0, 0, int(totalWidth), int(totalHeight)))
+	background := image.NewRGBA(image.Rect(0, 0, int(totalWidth+10), int(totalHeight+10)))
 	draw.Draw(background, background.Bounds(), image.White, image.Point{}, draw.Src)
 	backgroundSpirit := sprite.Sprite{
 		Name:     "background",
 		Image:    background,
 		Index:    0,
-		Position: image.Point{X: minX, Y: minY},
+		Position: image.Point{X: minX - 5, Y: minY - 5},
 	}
 	baseboard.AddSprite(&backgroundSpirit)