feat: 首页热门币种使用 CoinIcon 显示图标

✨ 修改内容：
- 首页热门币种 (hot_coins_section.dart): 使用 CoinIcon 替换 CircleAvatar
- BTC, ETH, SOL 等热门币种现在显示真实图标

🎨 效果：
- 热门币种列表显示真实的币种图标
- 提升视觉识别度和专业感

- ✅ Flutter Web 构建成功 (23.7s)

flutter_monisuo/build/web/flutter_bootstrap.js

@@ -37,6 +37,6 @@ _flutter.buildConfig = {"engineRevision":"e4b8dca3f1b4ede4c30371002441c88c12187e
 
 _flutter.loader.load({
   serviceWorkerSettings: {
-    serviceWorkerVersion: "3448837230" /* Flutter's service worker is deprecated and will be removed in a future Flutter release. */
+    serviceWorkerVersion: "3313231025" /* Flutter's service worker is deprecated and will be removed in a future Flutter release. */
   }
 });

flutter_monisuo/lib/ui/pages/home/hot_coins_section.dart

@@ -3,6 +3,7 @@ import 'package:shadcn_ui/shadcn_ui.dart';
 import '../../../core/theme/app_theme.dart';
 import '../../../core/theme/app_spacing.dart';
 import '../../../core/theme/app_theme_extension.dart';
+import '../../components/coin_icon.dart';
 
 /// 首頁熱門幣種區塊
 class HotCoinsSection extends StatelessWidget {
@@ -117,17 +118,10 @@ class _CoinRow extends StatelessWidget {
           // Left: avatar + name
           Row(
             children: [
-              CircleAvatar(
+              CoinIcon(
-                radius: 18,
+                symbol: symbol,
-                backgroundColor: context.colors.primary.withValues(alpha: 0.1),
+                size: 36,
-                child: Text(
+                isCircle: false,
-                  symbol,
-                  style: AppTextStyles.bodySmall(context).copyWith(
-                    fontSize: 10,
-                    fontWeight: FontWeight.w700,
-                    color: context.colors.primary,
-                  ),
-                ),
               ),
               const SizedBox(width: AppSpacing.sm + AppSpacing.xs),
               Column(