feat(playlist): 歌单集合页 + 歌单详情页 + 首页入口

style(ui): 播放页红心与标题居中对齐、标题单行

- playlists_page：歌单列表（封面/名称/歌曲数）、新建、重命名、删除
- playlist_detail_page：歌单内歌曲、播放全部、单曲播放、移除
- 首页"歌单列表"按钮接入 PlaylistsPage
- 播放页：标题行改为 center 对齐、标题限制单行，
  收藏按钮压到 36x36，红心与标题不再错位

lib/pages/player_page.dart

@@ -337,7 +337,7 @@ class _PlayerPageState extends BaseState<PlayerPage> {
 
           // ---- 标题 / 艺术家（收藏心在标题右侧）----
           Row(
-            crossAxisAlignment: CrossAxisAlignment.start,
+            crossAxisAlignment: CrossAxisAlignment.center,
             children: [
               Expanded(
                 child: Text(
@@ -348,7 +348,7 @@ class _PlayerPageState extends BaseState<PlayerPage> {
                     color: Colors.white,
                     height: 1.25,
                   ),
-                  maxLines: 2,
+                  maxLines: 1,
                   overflow: TextOverflow.ellipsis,
                 ),
               ),
@@ -356,17 +356,21 @@ class _PlayerPageState extends BaseState<PlayerPage> {
               IconButton(
                 onPressed: () => _toggleFavorite(song),
                 tooltip: '收藏',
+                padding: EdgeInsets.zero,
+                constraints:
+                    const BoxConstraints(minWidth: 36, minHeight: 36),
+                iconSize: 24,
                 icon: Icon(
                   _isFavorite ? Icons.favorite : Icons.favorite_border,
                   color: _isFavorite
                       ? const Color(0xFFE05C5C)
                       : Colors.white54,
-                  size: 26,
+                  size: 24,
                 ),
               ),
             ],
           ),
-          const SizedBox(height: 10),
+          const SizedBox(height: 2),
           Text(
             song.artist,
             style: TextStyle(fontSize: 16, color: Colors.grey[300]),