feat(cover): 支持横版封面并收紧底栏图标间距

- Drama 新增 coverLandscape，WatchProgress 新增 dramaCoverLandscape
- 继续观看横幅优先使用横版封面，缺省回退竖版
- 底部导航栏图标与文字间距由 5dp 收紧至 1dp

lib/core/data/models/drama.dart

@@ -97,6 +97,7 @@ class Drama {
     required this.title,
     required this.synopsis,
     required this.posterUrl,
+    this.coverLandscape = '',
     this.episodes = const [],
     this.titleLocales = const {},
     this.synopsisLocales = const {},
@@ -133,6 +134,9 @@ class Drama {
   final String tagCode;
   final String tagColor;
   final String posterUrl;
+
+  /// 横版封面，用于继续观看横幅等横向展示位；为空时回退竖版 `posterUrl`。
+  final String coverLandscape;
   final List<Episode> episodes;
   final String category;
   final Map<String, String> categoryLocales;
@@ -179,6 +183,7 @@ class Drama {
       tagCode: (json['tagCode'] as String? ?? '').trim(),
       tagColor: json['tagColor'] as String? ?? '',
       posterUrl: json['cover'] as String? ?? '',
+      coverLandscape: json['coverLandscape'] as String? ?? '',
       episodes: preview is Map<String, dynamic>
           ? [Episode.fromJson(preview)]
           : const [],
@@ -212,6 +217,7 @@ class Drama {
       tagCode: (json['tagCode'] as String? ?? '').trim(),
       tagColor: json['tagColor'] as String? ?? '',
       posterUrl: json['cover'] as String? ?? '',
+      coverLandscape: json['coverLandscape'] as String? ?? '',
       category: text.category,
       categoryLocales: text.categoryLocales,
       types: text.types,

lib/core/data/models/watch_progress.dart

@@ -16,6 +16,7 @@ class WatchProgress {
     this.dramaTitle,
     this.titleLocales = const {},
     this.dramaCover,
+    this.dramaCoverLandscape,
     this.episodeNumber,
     this.totalEpisodes,
     this.finished = false,
@@ -29,6 +30,9 @@ class WatchProgress {
   final String? dramaTitle;
   final Map<String, String> titleLocales;
   final String? dramaCover;
+
+  /// 横版封面，用于继续观看横幅等横向位；为空时回退 [dramaCover]。
+  final String? dramaCoverLandscape;
   final int? episodeNumber;
   final int? totalEpisodes;
   final Duration position;
@@ -60,6 +64,7 @@ class WatchProgress {
       dramaTitle: json['dramaTitle']?.toString(),
       titleLocales: localeMap(json['titleLocales']),
       dramaCover: json['dramaCover']?.toString(),
+      dramaCoverLandscape: json['dramaCoverLandscape']?.toString(),
       episodeNumber: json['episodeNumber'] == null
           ? null
           : jsonToInt(json['episodeNumber']),
@@ -83,6 +88,7 @@ class WatchProgress {
     if (dramaTitle != null) 'dramaTitle': dramaTitle,
     if (titleLocales.isNotEmpty) 'titleLocales': titleLocales,
     if (dramaCover != null) 'dramaCover': dramaCover,
+    if (dramaCoverLandscape != null) 'dramaCoverLandscape': dramaCoverLandscape,
     if (episodeNumber != null) 'episodeNumber': episodeNumber,
     if (totalEpisodes != null) 'totalEpisodes': totalEpisodes,
     'positionMs': position.inMilliseconds,

lib/core/data/models/watch_record.dart

@@ -46,6 +46,14 @@ class WatchRecord {
     return pageCover.isNotEmpty ? pageCover : drama?.posterUrl ?? '';
   }
 
+  /// 横向展示位（继续观看横幅）优先用横版封面，缺省回退竖版。
+  String get displayLandscapeCover {
+    final pageLandscape = progress.dramaCoverLandscape?.trim() ?? '';
+    if (pageLandscape.isNotEmpty) return pageLandscape;
+    final landscape = drama?.coverLandscape.trim() ?? '';
+    return landscape.isNotEmpty ? landscape : displayCover;
+  }
+
   /// 分页接口已带展示字段时无需等待详情加载。
   bool get hasDisplayMetadata =>
       displayTitle.isNotEmpty ||