feat(前端界面): WebUI新增连续阅读，优化缩放与窄屏显示

assets/webui/index.html

@@ -33,6 +33,7 @@
 				<button id="zoomInButton" class="icon-button" type="button" title="放大" disabled>+</button>
 				<button id="fitButton" class="button" type="button" data-short="宽" aria-label="适宽" disabled>适宽</button>
 				<button id="fitHeightButton" class="button" type="button" data-short="高" aria-label="适高" disabled>适高</button>
+				<button id="continuousButton" class="button" type="button" data-short="连" title="无间距连续显示" aria-label="无间距连续显示" aria-pressed="false" disabled>连续</button>
 				<button id="annotationButton" class="button" type="button" data-short="注" title="渲染注解" aria-label="渲染注解" aria-pressed="true">注解</button>
 			</div>
 			<div class="tool-group">