fix(ui): 移除所有人民币符号，统一使用积分值单位

- asset_page: 总资产估值改为显示"积分值"后缀
- asset_page: 估值占位符移除¥符号
- c2c_publish_page: 交易总额、单价、总额改为积分值单位

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mining-app/lib/presentation/pages/asset/asset_page.dart

@@ -356,7 +356,7 @@ class _AssetPageState extends ConsumerState<AssetPage> {
                 AmountText(
                   amount: displayValue != null ? formatAmount(displayValue) : null,
                   isLoading: isLoading,
-                  prefix: '¥ ',
+                  suffix: ' 积分值',
                   style: const TextStyle(
                     fontSize: 30,
                     fontWeight: FontWeight.bold,
@@ -630,7 +630,7 @@ class _AssetPageState extends ConsumerState<AssetPage> {
                   DataText(
                     data: isLoading ? null : '≈ $valueInCny',
                     isLoading: isLoading,
-                    placeholder: '≈ ¥--',
+                    placeholder: '≈ --',
                     style: TextStyle(
                       fontSize: 12,
                       color: AppColors.textMutedOf(context),

frontend/mining-app/lib/presentation/pages/c2c/c2c_publish_page.dart

@@ -629,7 +629,7 @@ class _C2cPublishPageState extends ConsumerState<C2cPublishPage> {
             children: [
               const Text('交易总额', style: TextStyle(fontSize: 14, color: _grayText)),
               Text(
-                '￥${formatAmount(total.toString())}',
+                '${formatAmount(total.toString())} 积分值',
                 style: const TextStyle(
                   fontSize: 18,
                   fontWeight: FontWeight.bold,
@@ -818,12 +818,12 @@ class _C2cPublishPageState extends ConsumerState<C2cPublishPage> {
           mainAxisSize: MainAxisSize.min,
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
-            Text('单价: ￥$price/积分值'),
+            Text('单价: $price 积分值'),
             const SizedBox(height: 8),
             Text('数量: $quantity 积分值'),
             const SizedBox(height: 8),
             Text(
-              '总额: ￥${formatAmount((double.parse(price) * double.parse(quantity)).toString())}',
+              '总额: ${formatAmount((double.parse(price) * double.parse(quantity)).toString())} 积分值',
               style: const TextStyle(fontWeight: FontWeight.bold),
             ),
             if (isSell) ...[