feat(缓存): 添加本地缓存功能并优化网络状态提示

实现本地缓存管理器，支持预加载开关和排行榜数据缓存
优化网络状态提示文案和错误处理
移除调试日志打印，改进用户体验

lib/controllers/load/locally.dart

@@ -0,0 +1,90 @@
+import 'dart:convert';
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// 时间: 2026-03-30
+/// 功能: 本地缓存管理器
+/// 介绍: 管理应用的本地缓存数据，包括排行榜数据等
+/// 最新变化: 新建本地缓存管理器
+
+class LocalCacheManager {
+  static final LocalCacheManager _instance = LocalCacheManager._internal();
+  factory LocalCacheManager() => _instance;
+  LocalCacheManager._internal();
+
+  static const String _preloadEnabledKey = 'preload_enabled';
+  static const String _popularListCachePrefix = 'popular_list_cache_';
+
+  /// 获取预加载开关状态
+  Future<bool> isPreloadEnabled() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(_preloadEnabledKey) ?? true;
+  }
+
+  /// 设置预加载开关状态
+  Future<void> setPreloadEnabled(bool enabled) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_preloadEnabledKey, enabled);
+  }
+
+  /// 缓存排行榜数据
+  Future<void> cachePopularList(
+    String type,
+    List<Map<String, dynamic>> data,
+  ) async {
+    final prefs = await SharedPreferences.getInstance();
+    final key = _popularListCachePrefix + type;
+    final jsonData = jsonEncode(data);
+    await prefs.setString(key, jsonData);
+
+    final timestampKey = '${key}_timestamp';
+    await prefs.setInt(timestampKey, DateTime.now().millisecondsSinceEpoch);
+  }
+
+  /// 获取缓存的排行榜数据
+  Future<List<Map<String, dynamic>>?> getCachedPopularList(String type) async {
+    final prefs = await SharedPreferences.getInstance();
+    final key = _popularListCachePrefix + type;
+    final jsonData = prefs.getString(key);
+
+    if (jsonData == null) {
+      return null;
+    }
+
+    try {
+      final decoded = jsonDecode(jsonData);
+      if (decoded is List) {
+        return decoded.cast<Map<String, dynamic>>();
+      }
+    } catch (e) {
+      print('解析缓存数据失败: $e');
+    }
+
+    return null;
+  }
+
+  /// 获取缓存时间戳
+  Future<int?> getCacheTimestamp(String type) async {
+    final prefs = await SharedPreferences.getInstance();
+    final key = '${_popularListCachePrefix}${type}_timestamp';
+    return prefs.getInt(key);
+  }
+
+  /// 清除指定类型的缓存
+  Future<void> clearCache(String type) async {
+    final prefs = await SharedPreferences.getInstance();
+    final key = _popularListCachePrefix + type;
+    await prefs.remove(key);
+    await prefs.remove('${key}_timestamp');
+  }
+
+  /// 清除所有排行榜缓存
+  Future<void> clearAllPopularCache() async {
+    final prefs = await SharedPreferences.getInstance();
+    final keys = prefs.getKeys();
+    for (final key in keys) {
+      if (key.startsWith(_popularListCachePrefix)) {
+        await prefs.remove(key);
+      }
+    }
+  }
+}