feat(mining-app): 提升价格显示小数精度

- K线详情弹窗(开/高/低/收)：小数位数增加5位
  - 价格≥1: 4位 → 9位
  - 价格0.0001~1: 6位 → 11位
  - 超小价格有效数字: 4位 → 9位
- 兑换页面"当前积分股价值"：小数位数增加2位
  - formatPriceFull 新增 extraDecimals 可选参数，支持按需增加精度
  - 调用时传入 extraDecimals: 2
- 资产页面"总资产估值"：小数位数从4位增加到6位
  - formatAmount(4位) → formatDecimal(6位)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/mining-app/lib/core/utils/format_utils.dart

@@ -71,12 +71,13 @@ String formatPrice(String? value) {
 }
 
 /// 与 formatPrice 相同逻辑，但不使用 0.0{n} 缩写，直接展示完整的0
-String formatPriceFull(String? value) {
+/// [extraDecimals] 可额外增加小数位数
+String formatPriceFull(String? value, {int extraDecimals = 0}) {
   if (value == null || value.isEmpty) return '0';
   try {
     final decimal = Decimal.parse(value);
-    if (decimal >= Decimal.one) return decimal.toStringAsFixed(4);
-    if (decimal >= Decimal.parse('0.0001')) return decimal.toStringAsFixed(6);
+    if (decimal >= Decimal.one) return decimal.toStringAsFixed(4 + extraDecimals);
+    if (decimal >= Decimal.parse('0.0001')) return decimal.toStringAsFixed(6 + extraDecimals);
     if (decimal <= Decimal.zero) return '0';
     final str = decimal.toStringAsFixed(18);
     final dotIndex = str.indexOf('.');
@@ -88,8 +89,8 @@ String formatPriceFull(String? value) {
         break;
       }
     }
-    // 截取到前导零 + 7位有效数字
-    final sigEnd = dotIndex + 1 + zeroCount + 7;
+    // 截取到前导零 + 7位有效数字 + extraDecimals
+    final sigEnd = dotIndex + 1 + zeroCount + 7 + extraDecimals;
     final end = sigEnd > str.length ? str.length : sigEnd;
     return str.substring(0, end);
   } catch (e) {

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

@@ -366,7 +366,7 @@ class _AssetPageState extends ConsumerState<AssetPage> {
                 const SizedBox(height: 8),
                 // 金额 - 实时刷新显示
                 AmountText(
-                  amount: displayValue != null ? formatAmount(displayValue) : null,
+                  amount: displayValue != null ? formatDecimal(displayValue, 6) : null,
                   isLoading: isLoading,
                   suffix: ' 积分值',
                   style: const TextStyle(

frontend/mining-app/lib/presentation/pages/trading/trading_page.dart

@@ -214,7 +214,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
             textBaseline: TextBaseline.alphabetic,
             children: [
               AmountText(
-                amount: priceInfo != null ? formatPriceFull(price) : null,
+                amount: priceInfo != null ? formatPriceFull(price, extraDecimals: 2) : null,
                 isLoading: isLoading,
                 style: const TextStyle(
                   fontSize: 30,

frontend/mining-app/lib/presentation/widgets/kline_chart/kline_chart_widget.dart

@@ -728,8 +728,8 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
   }
 
   String _formatPrice(double price) {
-    if (price >= 1) return price.toStringAsFixed(4);
-    if (price >= 0.0001) return price.toStringAsFixed(6);
+    if (price >= 1) return price.toStringAsFixed(9);
+    if (price >= 0.0001) return price.toStringAsFixed(11);
     if (price <= 0) return '0';
     // 0.00000980 → 0.0{5}980
     final str = price.toStringAsFixed(18);
@@ -743,7 +743,7 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
       }
     }
     final sigStart = dotIndex + 1 + zeroCount;
-    final sigEnd = math.min(sigStart + 4, str.length);
+    final sigEnd = math.min(sigStart + 9, str.length);
     final significant = str.substring(sigStart, sigEnd);
     return '0.0{$zeroCount}$significant';
   }