refactor: 优化后台管理界面布局与侧边栏样式

src/lib/components/admin/MarkdownEditor.svelte

@@ -441,7 +441,8 @@
 	.md-toolbar {
 		/* 吸顶：紧贴后台固定顶栏（高度 58px）下方，滚动时保持可见 */
 		position: sticky;
-		top: 58px;
+		top: 0px;
+		/* 移动端需要额外 offset 请在 media query 中处理 */
 		/* 编辑器 .cm-scroller 是 position: relative + z-index: 0，且 DOM 更靠后，
 		   必须抬高层级，否则正文会盖在工具条上（看起来像半透明） */
 		z-index: 20;

src/routes/admin/+layout.svelte

@@ -5,7 +5,6 @@
 	import {
 		ExternalLink,
 		Menu,
-		Plus,
 		LayoutDashboard,
 		FileText,
 		AppWindow,
@@ -58,17 +57,9 @@
 			</a>
 		</div>
 
-		<div class="sidebar-action">
-			<a href={resolve('/admin/posts/new')} class="btn-new">
-				<Plus size={18} />
-				<span>撰写新内容...</span>
-			</a>
-		</div>
-
 		<div class="sidebar-scrollable">
 			<nav class="sidebar-nav">
 				<div class="nav-group">
-					<div class="nav-group-title">主控制台</div>
 					<a
 						href={resolve('/admin')}
 						class="nav-item {$page.url.pathname === '/admin' ? 'active' : ''}"
@@ -126,7 +117,7 @@
 				</div>
 
 				<div class="nav-group">
-					<div class="nav-group-title">资源与系统</div>
+					<div class="nav-group-title">资源库</div>
 					<a
 						href={resolve('/admin/files')}
 						class="nav-item {$page.url.pathname.startsWith('/admin/files') ? 'active' : ''}"
@@ -134,18 +125,19 @@
 						<ImageIcon size={18} />
 						<span>媒体与文件</span>
 					</a>
-					<a
-						href={resolve('/admin/settings')}
-						class="nav-item {$page.url.pathname.startsWith('/admin/settings') ? 'active' : ''}"
-					>
-						<Settings size={18} />
-						<span>站点设置</span>
-					</a>
 				</div>
 			</nav>
 		</div>
 
 		<div class="sidebar-footer">
+			<a
+				href={resolve('/admin/settings')}
+				class="site-link {$page.url.pathname.startsWith('/admin/settings') ? 'active' : ''}"
+				title="站点设置"
+			>
+				<Settings size={15} aria-hidden="true" />
+				<span>站点设置</span>
+			</a>
 			<a href={resolve('/')} target="_blank" class="site-link" title="访问前台">
 				<ExternalLink size={15} aria-hidden="true" />
 				<span>访问前台</span>
@@ -230,35 +222,6 @@
 		text-transform: uppercase;
 	}
 
-	.sidebar-action {
-		padding: 24px;
-		border-bottom: 1px solid #222;
-	}
-
-	.btn-new {
-		display: flex;
-		align-items: center;
-		justify-content: center;
-		gap: 8px;
-		width: 100%;
-		padding: 12px 14px;
-		background: #222;
-		color: #fff;
-		font-weight: 600;
-		font-size: 0.95rem;
-		text-decoration: none;
-		text-transform: uppercase;
-		letter-spacing: 1px;
-		border: 1px solid #333;
-		transition: all 0.2s ease;
-	}
-
-	.btn-new:hover {
-		background-color: var(--accent-color, #419b38);
-		border-color: var(--accent-color, #419b38);
-		color: white;
-	}
-
 	.sidebar-scrollable {
 		flex: 1;
 		overflow-y: auto;
@@ -303,6 +266,8 @@
 
 	.nav-item:hover {
 		color: var(--accent-color, #419b38);
+		background: rgba(255, 255, 255, 0.03);
+		border-left: 2px solid var(--accent-color, #419b38);
 	}
 
 	.nav-item.active {
@@ -333,7 +298,8 @@
 		letter-spacing: 0.5px;
 	}
 
-	.site-link:hover {
+	.site-link:hover,
+	.site-link.active {
 		color: var(--accent-color, #419b38);
 	}
 
@@ -393,7 +359,7 @@
 	.content-area {
 		flex: 1;
 		padding: 32px 40px;
-		overflow-x: hidden;
+		/* overflow-x: hidden is removed because it breaks position: sticky for descendants (toolbar/sidebar) */
 	}
 
 	.admin-container {

src/routes/admin/posts/[id]/+page.svelte

@@ -364,7 +364,7 @@
 
 	.form-sidebar {
 		position: sticky;
-		top: 80px;
+		top: 20px;
 		width: 100%;
 		display: flex;
 		flex-direction: column;

src/routes/admin/posts/new/+page.svelte

@@ -394,7 +394,7 @@
 
 	.form-sidebar {
 		position: sticky;
-		top: 80px;
+		top: 20px;
 		width: 100%;
 		display: flex;
 		flex-direction: column;