style(ui): 播放页指示器改为"当前页长条"样式 + 补齐底部安全区

指示器（按设计稿）：
- 三段：左点 / 中条 / 右点
- 当前页对应的段展开为 30x7 长条并高亮白色，
  另外两段收起为 7x7 小点（暗）
- 主页=中间长条，信息页=左长条，歌词页=右长条，220ms 动画过渡
- 点击任一段可直接跳到对应页

安全区：
- PageView 外层包 SafeArea(top: false)，
  控制按钮不再贴着 mback 手势区

lib/pages/player_page.dart

@@ -249,21 +249,25 @@ class _PlayerPageState extends BaseState<PlayerPage> {
           ),
         ],
       ),
-      body: PageView(
-        controller: _pageController,
-        onPageChanged: (index) => setState(() => _pageIndex = index),
-        children: [
-          _buildInfoPage(song),
-          _buildMainPage(service, song, isPlaying),
-          _buildLyricsPage(song),
-        ],
+      body: SafeArea(
+        top: false,
+        child: PageView(
+          controller: _pageController,
+          onPageChanged: (index) => setState(() => _pageIndex = index),
+          children: [
+            _buildInfoPage(song),
+            _buildMainPage(service, song, isPlaying),
+            _buildLyricsPage(song),
+          ],
+        ),
       ),
     );
   }
 
-  /// 顶部两点指示器：左点=信息页，右点=歌词页，中间不亮表示在主页
+  /// 顶部指示器：当前页对应"长条"，另外两页是小点。
+  /// 主页=中间长条，信息页=左长条，歌词页=右长条。
   Widget _buildPageIndicator() {
-    Widget dot(int index) {
+    Widget segment(int index) {
       final active = _pageIndex == index;
       return GestureDetector(
         onTap: () => _pageController.animateToPage(
@@ -271,13 +275,18 @@ class _PlayerPageState extends BaseState<PlayerPage> {
           duration: const Duration(milliseconds: 280),
           curve: Curves.easeOutCubic,
         ),
-        child: AnimatedContainer(
-          duration: const Duration(milliseconds: 200),
-          width: 7,
-          height: 7,
-          decoration: BoxDecoration(
-            shape: BoxShape.circle,
-            color: active ? Colors.white : Colors.white24,
+        behavior: HitTestBehavior.opaque,
+        child: Padding(
+          padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 2),
+          child: AnimatedContainer(
+            duration: const Duration(milliseconds: 220),
+            curve: Curves.easeOutCubic,
+            width: active ? 30 : 7,
+            height: 7,
+            decoration: BoxDecoration(
+              color: active ? Colors.white : Colors.white24,
+              borderRadius: BorderRadius.circular(4),
+            ),
           ),
         ),
       );
@@ -286,14 +295,11 @@ class _PlayerPageState extends BaseState<PlayerPage> {
     return Row(
       mainAxisSize: MainAxisSize.min,
       children: [
-        dot(0),
-        Container(
-          width: 56,
-          height: 1,
-          margin: const EdgeInsets.symmetric(horizontal: 8),
-          color: Colors.white12,
-        ),
-        dot(2),
+        segment(0),
+        const SizedBox(width: 6),
+        segment(1),
+        const SizedBox(width: 6),
+        segment(2),
       ],
     );
   }