style(ui): 收紧媒体库内部间距

- WebDAV 卡片与"本地音乐/最近播放"之间：24 -> 12
- 按钮行与"我的收藏"标题之间：32 -> 16

lib/pages/home_page.dart

@@ -847,7 +847,7 @@ class _HomePageState extends BaseState<HomePage> {
                               ],
                             ),
                           ),
-                          const SizedBox(height: 24),
+                          const SizedBox(height: 12),
                           Row(
                             children: [
                               Expanded(
@@ -907,7 +907,7 @@ class _HomePageState extends BaseState<HomePage> {
                               ),
                             ],
                           ),
-                          const SizedBox(height: 32),
+                          const SizedBox(height: 16),
                         ],
                       ),
                     ),