refactor(apps): 主题系统迁移至 ColorScheme + 扩展架构并支持 Dark Mode

apps/lib/data/cache/memory_cache_store.dart

@@ -0,0 +1,24 @@
+import 'cache_store.dart';
+
+class MemoryCacheStore implements CacheStore {
+  final Map<String, Object?> _values = <String, Object?>{};
+
+  @override
+  Future<T?> read<T>(String key) async {
+    final value = _values[key];
+    if (value is T) {
+      return value;
+    }
+    return null;
+  }
+
+  @override
+  Future<void> write<T>(String key, T value) async {
+    _values[key] = value;
+  }
+
+  @override
+  Future<void> remove(String key) async {
+    _values.remove(key);
+  }
+}