feat(前端界面): 优化滚动条样式，配色更轻盈协调

assets/webui/ofdgo.css

@@ -285,6 +285,13 @@ body[data-hide-meta] .meta-panel {
 	display: none;
 }
 
+.page-list-panel,
+.viewer-panel,
+.meta-panel {
+	scrollbar-width: thin;
+	scrollbar-color: var(--line-strong) transparent;
+}
+
 .page-list-panel,
 .meta-panel {
 	min-height: 0;

assets/webui/ofdgo.js

@@ -2517,6 +2517,7 @@ function scrollbarWidth() {
 	probe.style.width = "100px";
 	probe.style.height = "100px";
 	probe.style.overflow = "scroll";
+	probe.style.scrollbarWidth = getComputedStyle(el.viewerPanel).scrollbarWidth;
 	probe.style.left = "-9999px";
 	document.body.append(probe);
 	const width = probe.offsetWidth - probe.clientWidth;

ofdgo_renderer_image.go

@@ -310,13 +310,15 @@ func imageWithTransparentEdge(img image.Image) (image.Image, int) {
 	src, ok := source.(*image.NRGBA)
 	if ok {
 		srcBounds := src.Bounds()
+		hasZero = src.Pix[3] == 0
+		hasVisible = !hasZero
+	scan:
 		for y := srcBounds.Min.Y; y < srcBounds.Max.Y; y++ {
 			offset := src.PixOffset(srcBounds.Min.X, y) + 3
 			for x := 0; x < w; x++ {
-				if src.Pix[offset] == 0 {
-					hasZero = true
-				} else {
-					hasVisible = true
+				if (src.Pix[offset] == 0) != hasZero {
+					hasZero, hasVisible = true, true
+					break scan
 				}
 				offset += 4
 			}