feat(recommend): 上新板块改按后端语义码判断，顶部轮播改为无缝循环

Drama 新增 tagCode，推荐页只看 NEW_ARRIVAL 这个码决定上新横滑，
不再依赖可变的标签文案；分类网格高度改为复用卡片的统一常量。
头部轮播改用虚拟无限页码，首尾相接且能反向滑，自动播放不再倒滑回第一张。

lib/core/data/models/drama.dart

@@ -102,6 +102,7 @@ class Drama {
     this.synopsisLocales = const {},
     this.tag = '',
     this.tagLocales = const {},
+    this.tagCode = '',
     this.tagColor = '',
     this.category = '',
     this.categoryLocales = const {},
@@ -127,6 +128,9 @@ class Drama {
   final Map<String, String> synopsisLocales;
   final String tag;
   final Map<String, String> tagLocales;
+
+  /// 标签语义码（如 `NEW_ARRIVAL`）。文案会随语言变，语义判断只认这个码。
+  final String tagCode;
   final String tagColor;
   final String posterUrl;
   final List<Episode> episodes;
@@ -172,6 +176,7 @@ class Drama {
       synopsisLocales: text.synopsisLocales,
       tag: text.tag,
       tagLocales: text.tagLocales,
+      tagCode: (json['tagCode'] as String? ?? '').trim(),
       tagColor: json['tagColor'] as String? ?? '',
       posterUrl: json['cover'] as String? ?? '',
       episodes: preview is Map<String, dynamic>
@@ -204,6 +209,7 @@ class Drama {
       synopsisLocales: text.synopsisLocales,
       tag: text.tag,
       tagLocales: text.tagLocales,
+      tagCode: (json['tagCode'] as String? ?? '').trim(),
       tagColor: json['tagColor'] as String? ?? '',
       posterUrl: json['cover'] as String? ?? '',
       category: text.category,
@@ -315,7 +321,10 @@ class _DramaText {
     final category = _firstText(categoryLocales, json['category'], types);
     return _DramaText(
       title: _firstText(titleLocales, json['title']),
-      synopsis: _firstText(synopsisLocales, json['synopsis'] ?? json['description']),
+      synopsis: _firstText(
+        synopsisLocales,
+        json['synopsis'] ?? json['description'],
+      ),
       titleLocales: titleLocales,
       synopsisLocales: synopsisLocales,
       tag: _firstText(tagLocales, json['tag']),
@@ -328,7 +337,11 @@ class _DramaText {
   }
 }
 
-String _firstText(Map<String, String> locales, Object? fallback, [List<Map<String, String>>? types]) {
+String _firstText(
+  Map<String, String> locales,
+  Object? fallback, [
+  List<Map<String, String>>? types,
+]) {
   final chinese = locales['zh'] ?? '';
   if (chinese.isNotEmpty) return chinese;
   if (types != null && types.isNotEmpty) {
@@ -339,7 +352,9 @@ String _firstText(Map<String, String> locales, Object? fallback, [List<Map<Strin
 }
 
 String _genreText(List<Map<String, String>> types, Object? fallback) {
-  final names = types.map((item) => item['zh'] ?? '').where((value) => value.isNotEmpty);
+  final names = types
+      .map((item) => item['zh'] ?? '')
+      .where((value) => value.isNotEmpty);
   final joined = names.join(' / ');
   if (joined.isNotEmpty) return joined;
   return fallback is String ? fallback : '';