feat(界面设计): 精简设置布局，修正标题栏遮罩

assets/webui/index.html

@@ -455,7 +455,6 @@
 					</nav>
 					<div class="appearance-content">
 						<section data-appearance-page="theme">
-							<div class="appearance-label">外观主题</div>
 							<div class="appearance-themes">
 								<button type="button" data-theme-choice="system"><span class="theme-system-icon"></span><span>系统</span></button>
 								<button type="button" data-theme-choice="light"><span class="theme-light-icon"></span><span>浅色</span></button>
@@ -463,7 +462,6 @@
 							</div>
 						</section>
 						<section id="associationSection" data-appearance-page="association" hidden>
-							<div class="appearance-label">文件关联</div>
 							<div class="association-row" data-scope="user"><span>当前用户</span><span class="association-state"></span><div class="association-actions"><button class="small-button" type="button" data-action="register">注册</button><button class="small-button" type="button" data-action="remove">撤销</button></div></div>
 							<div class="association-row" data-scope="machine"><span>所有用户</span><span class="association-state"></span><div class="association-actions"><button class="small-button" type="button" data-action="register">注册</button><button class="small-button" type="button" data-action="remove">撤销</button></div></div>
 							<div id="associationMessage" class="form-status" hidden></div>