feat(前端界面): 完善键盘操作，优化阅读与搜索体验

assets/webui/ofdgo.css

@@ -659,6 +659,11 @@ button.outline-link:hover {
 	overflow-y: hidden;
 }
 
+.viewer-panel:focus-visible {
+	outline: 2px solid var(--focus);
+	outline-offset: -2px;
+}
+
 .viewer-panel.pan-mode,
 .pan-mode .text-run > span {
 	cursor: grab;