fix(mining-app): 价格显示优化 + 涨跌幅精度再提升

- 兑换页顶部价格改用 formatPriceFull 显示完整零（不再用 0.0{n} 缩写）
- K线纵坐标有效数字从7位精简为4位，节省空间更简洁
- 涨跌幅精度再提升：后端 toFixed(8)→toFixed(12)，前端 6位→10位小数

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

backend/services/trading-service/src/application/services/price.service.ts

@@ -104,8 +104,8 @@ export class PriceService {
       burnMultiplier: burnMultiplier.toFixed(18),
       minuteBurnRate: minuteBurnRate.toFixed(18),
       snapshotTime: new Date(),
-      // 保留8位小数，确保每分钟销毁带来的微小涨幅在前端可见
-      priceChangePercent: priceChangePercent.toFixed(8),
+      // 保留12位小数，确保每分钟销毁带来的微小涨幅在前端可见
+      priceChangePercent: priceChangePercent.toFixed(12),
       initialPrice: initialPrice.toFixed(18),
     };
   }
@@ -265,8 +265,8 @@ export class PriceService {
       burnMultiplier: burnMultiplier.toFixed(18),
       minuteBurnRate: snapshot.minuteBurnRate.toFixed(18),
       snapshotTime: snapshot.snapshotTime,
-      // 保留8位小数，确保每分钟销毁带来的微小涨幅在前端可见
-      priceChangePercent: priceChangePercent.toFixed(8),
+      // 保留12位小数，确保每分钟销毁带来的微小涨幅在前端可见
+      priceChangePercent: priceChangePercent.toFixed(12),
       initialPrice: initialPrice.toFixed(18),
     };
   }

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

@@ -70,6 +70,33 @@ 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) {
+  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.zero) return '0';
+    final str = decimal.toStringAsFixed(18);
+    final dotIndex = str.indexOf('.');
+    int zeroCount = 0;
+    for (int i = dotIndex + 1; i < str.length; i++) {
+      if (str[i] == '0') {
+        zeroCount++;
+      } else {
+        break;
+      }
+    }
+    // 截取到前导零 + 7位有效数字
+    final sigEnd = dotIndex + 1 + zeroCount + 7;
+    final end = sigEnd > str.length ? str.length : sigEnd;
+    return str.substring(0, end);
+  } catch (e) {
+    return '0';
+  }
+}
+
 String formatAmount(String? value) {
   return formatDecimal(value, 4);
 }

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

@@ -179,7 +179,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
             textBaseline: TextBaseline.alphabetic,
             children: [
               AmountText(
-                amount: priceInfo != null ? formatPrice(price) : null,
+                amount: priceInfo != null ? formatPriceFull(price) : null,
                 isLoading: isLoading,
                 style: const TextStyle(
                   fontSize: 30,
@@ -219,8 +219,8 @@ class _TradingPageState extends ConsumerState<TradingPage> {
                     ),
                     const SizedBox(width: 4),
                     DataText(
-                      // 显示6位小数，确保每分钟销毁引起的涨幅尾数可见
-                      data: isLoading ? null : '$sign${changePercent.toStringAsFixed(6)}%',
+                      // 显示10位小数，确保每分钟销毁引起的涨幅尾数可见
+                      data: isLoading ? null : '$sign${changePercent.toStringAsFixed(10)}%',
                       isLoading: isLoading,
                       placeholder: '+--.--%',
                       style: TextStyle(

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

@@ -743,7 +743,7 @@ class _KlineChartWidgetState extends State<KlineChartWidget> {
       }
     }
     final sigStart = dotIndex + 1 + zeroCount;
-    final sigEnd = math.min(sigStart + 7, str.length);
+    final sigEnd = math.min(sigStart + 4, str.length);
     final significant = str.substring(sigStart, sigEnd);
     return '0.0{$zeroCount}$significant';
   }

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

@@ -567,7 +567,7 @@ class KlinePainter extends CustomPainter {
       }
     }
     final sigStart = dotIndex + 1 + zeroCount;
-    final sigEnd = math.min(sigStart + 7, str.length);
+    final sigEnd = math.min(sigStart + 4, str.length);
     final significant = str.substring(sigStart, sigEnd);
     return '0.0{$zeroCount}$significant';
   }