feat(flutter): 统一二级页头并恢复新剧暖色

lib/core/widgets/plain_page_scaffold.dart

@@ -3,6 +3,7 @@
 import 'package:flutter/material.dart';
 
 import '../theme/app_colors.dart';
+import 'subpage_header.dart';
 
 /// 二级页面通用骨架：返回栏 + 标题/副标题 + 可滚动内容，无底部导航。
 class PlainPageScaffold extends StatelessWidget {
@@ -30,47 +31,11 @@ class PlainPageScaffold extends StatelessWidget {
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
-            Padding(
-              padding: const EdgeInsets.fromLTRB(6, 4, 14, 0),
-              child: Row(
-                children: [
-                  IconButton(
-                    key: backKey,
-                    tooltip: MaterialLocalizations.of(
-                      context,
-                    ).backButtonTooltip,
-                    onPressed: () => Navigator.of(context).maybePop(),
-                    icon: const Icon(
-                      Icons.chevron_left_rounded,
-                      color: AppColors.onSurface,
-                      size: 26,
-                    ),
-                  ),
-                  Expanded(
-                    child: Text(
-                      title,
-                      maxLines: 1,
-                      overflow: TextOverflow.ellipsis,
-                      style: const TextStyle(
-                        color: AppColors.onSurface,
-                        fontSize: 20,
-                        fontWeight: FontWeight.w800,
-                      ),
-                    ),
-                  ),
-                ],
-              ),
+            AppSubpageHeader(
+              title: title,
+              subtitle: subtitle,
+              backKey: backKey,
             ),
-            if (subtitle != null)
-              Padding(
-                padding: const EdgeInsets.fromLTRB(16, 0, 16, 8),
-                child: Text(
-                  subtitle!,
-                  maxLines: 2,
-                  overflow: TextOverflow.ellipsis,
-                  style: const TextStyle(color: AppColors.muted, fontSize: 12),
-                ),
-              ),
             Expanded(child: child),
           ],
         ),

lib/core/widgets/subpage_header.dart

@@ -0,0 +1,130 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+
+import '../theme/app_colors.dart';
+
+const double _height = 52;
+const double _heightWithSubtitle = 64;
+const double _horizontal = 14;
+const double _backSize = 36;
+const double _backGap = 12;
+const double _titleFontSize = 18;
+const double _subtitleFontSize = 12;
+const double _actionGap = 8;
+const double _iconSize = 20;
+
+/// 二级页面统一返回按钮，浅色页使用 card 圆底，深色页使用透明底。
+class AppSubpageBackButton extends StatelessWidget {
+  const AppSubpageBackButton({
+    super.key,
+    required this.backKey,
+    this.dark = false,
+    this.onBack,
+  });
+
+  final Key backKey;
+  final bool dark;
+  final VoidCallback? onBack;
+
+  @override
+  Widget build(BuildContext context) {
+    return SizedBox(
+      key: backKey,
+      width: _backSize,
+      height: _backSize,
+      child: Tooltip(
+        message: MaterialLocalizations.of(context).backButtonTooltip,
+        child: Material(
+          color: dark ? Colors.transparent : AppColors.card,
+          shape: const CircleBorder(),
+          clipBehavior: Clip.antiAlias,
+          child: InkWell(
+            onTap: onBack ?? () => Navigator.of(context).maybePop(),
+            child: Icon(
+              Icons.chevron_left_rounded,
+              color: dark ? Colors.white : AppColors.onSurface,
+              size: _iconSize,
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+/// 二级页面统一页头：返回按钮、左对齐标题、可选副标题与右侧操作。
+class AppSubpageHeader extends StatelessWidget {
+  const AppSubpageHeader({
+    super.key,
+    required this.title,
+    required this.backKey,
+    this.subtitle,
+    this.actions,
+    this.onBack,
+    this.dark = false,
+  });
+
+  final String title;
+  final Key backKey;
+  final String? subtitle;
+  final Widget? actions;
+  final VoidCallback? onBack;
+  final bool dark;
+
+  @override
+  Widget build(BuildContext context) {
+    final foreground = dark ? Colors.white : AppColors.onSurface;
+    final secondary = dark ? Colors.white70 : AppColors.muted;
+    return SizedBox(
+      key: const Key('subpage-header'),
+      height: subtitle == null ? _height : _heightWithSubtitle,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: _horizontal),
+        child: Row(
+          children: [
+            AppSubpageBackButton(backKey: backKey, dark: dark, onBack: onBack),
+            const SizedBox(width: _backGap),
+            Expanded(
+              child: Column(
+                mainAxisAlignment: MainAxisAlignment.center,
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    title,
+                    key: const Key('subpage-title'),
+                    maxLines: 1,
+                    overflow: TextOverflow.ellipsis,
+                    style: TextStyle(
+                      color: foreground,
+                      fontSize: _titleFontSize,
+                      fontWeight: FontWeight.w800,
+                    ),
+                  ),
+                  if (subtitle != null) ...[
+                    const SizedBox(height: 2),
+                    Text(
+                      subtitle!,
+                      key: const Key('subpage-subtitle'),
+                      maxLines: 1,
+                      overflow: TextOverflow.ellipsis,
+                      style: TextStyle(
+                        color: secondary,
+                        fontSize: _subtitleFontSize,
+                        fontWeight: FontWeight.w500,
+                      ),
+                    ),
+                  ],
+                ],
+              ),
+            ),
+            if (actions != null) ...[
+              const SizedBox(width: _actionGap),
+              actions!,
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}