refactor: 优化后台设置页面结构与样式

src/routes/admin/settings/+page.svelte

@@ -64,7 +64,6 @@
 <div class="settings-container">
 	{#if activeTab === 'basic'}
 		<div class="settings-card full-width" style="margin-bottom: 25px;">
-			<div class="settings-section" style="padding: 0;">
 			<h3>系统与安全环境</h3>
 			<div class="info-grid">
 				<div class="info-item">
@@ -89,7 +88,6 @@
 				</div>
 			</div>
 		</div>
-		</div>
 
 		<div class="settings-card full-width">
 			<form
@@ -234,7 +232,6 @@
 
 	{#if activeTab === 'appearance'}
 		<div class="settings-card full-width">
-			<div class="settings-section">
 			<h3>首页顶部主图与外观偏好</h3>
 
 			<form
@@ -280,12 +277,10 @@
 				</div>
 			</form>
 		</div>
-		</div>
 	{/if}
 
 	{#if activeTab === 'terms'}
 		<div class="settings-card full-width">
-			<div class="settings-section">
 			<h3>个性化术语设定</h3>
 			<p class="desc">
 				您可以根据部署场景（如教学系统、文档库）自定义后台各模块的显示名称，例如将“文章”改为“实验手册”。
@@ -362,7 +357,6 @@
 				</div>
 			</form>
 		</div>
-		</div>
 	{:else if activeTab === 'analytics'}
 		<AnalyticsPanel analyticsPromise={data.analytics} />
 	{/if}
@@ -448,14 +442,16 @@
 		word-break: break-word;
 	}
 
-	.settings-card h3 {
+	.settings-card > h3 {
-		margin: 0 0 16px 0;
+		margin: 0 0 12px 0;
 		font-size: 1.2rem;
+		border-bottom: 1px solid var(--border-color, rgba(0, 0, 0, 0.1));
+		padding-bottom: 10px;
 		color: var(--text-color);
-		font-weight: 600;
 	}
 
-	.settings-section .desc {
+	.settings-section .desc,
+	.settings-card > .desc {
 		font-size: 0.9rem;
 		color: var(--text-muted, rgba(0, 0, 0, 0.6));
 		margin-bottom: 24px;