fix(mining-app): 优化页面文案与涨跌幅精度

- 兑换页顶部隐藏价格后方"积分值"文字，界面更简洁
- 兑换页"较上线首日"涨跌幅精度从2位小数提升至6位，每分钟销毁引起的涨幅尾数可见
- 兑换页"黑洞销毁量"文案改为"已销毁量"，更直观易懂
- 贡献值页"积分股池实时余量"文案改为"100亿销毁剩余量"
- 后端 priceChangePercent 精度从 toFixed(2) 提升至 toFixed(8)，支持前端高精度显示

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

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

@@ -104,7 +104,8 @@ export class PriceService {
       burnMultiplier: burnMultiplier.toFixed(18),
       minuteBurnRate: minuteBurnRate.toFixed(18),
       snapshotTime: new Date(),
-      priceChangePercent: priceChangePercent.toFixed(2),
+      // 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),
       initialPrice: initialPrice.toFixed(18),
     };
   }
@@ -264,7 +265,8 @@ export class PriceService {
       burnMultiplier: burnMultiplier.toFixed(18),
       minuteBurnRate: snapshot.minuteBurnRate.toFixed(18),
       snapshotTime: snapshot.snapshotTime,
-      priceChangePercent: priceChangePercent.toFixed(2),
+      // 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),
       initialPrice: initialPrice.toFixed(18),
     };
   }

frontend/mining-app/lib/presentation/pages/contribution/contribution_page.dart

@@ -207,11 +207,11 @@ class ContributionPage extends ConsumerWidget {
             ),
           ),
           const SizedBox(height: 12),
-          // 积分股池实时余量
+          // 100亿销毁剩余量
           Row(
             children: [
               Text(
-                '积分股池实时余量: ',
+                '100亿销毁剩余量: ',
                 style: TextStyle(fontSize: 12, color: AppColors.textSecondaryOf(context)),
               ),
               isSharePoolLoading

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

@@ -188,15 +188,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
                   letterSpacing: -0.75,
                 ),
               ),
-              const SizedBox(width: 4),
+              // '积分值' 文字已隐藏
-              Text(
-                '积分值',
-                style: TextStyle(
-                  fontSize: 14,
-                  fontWeight: FontWeight.w500,
-                  color: AppColors.textSecondaryOf(context),
-                ),
-              ),
             ],
           ),
           const SizedBox(height: 8),
@@ -227,7 +219,8 @@ class _TradingPageState extends ConsumerState<TradingPage> {
                     ),
                     const SizedBox(width: 4),
                     DataText(
-                      data: isLoading ? null : '$sign${changePercent.toStringAsFixed(2)}%',
+                      // 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)}%',
                       isLoading: isLoading,
                       placeholder: '+--.--%',
                       style: TextStyle(
@@ -357,7 +350,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
               Container(width: 1, height: 24, color: bgGray),
               const SizedBox(width: 16),
               _buildMarketDataItem(
-                '黑洞销毁量',
+                '已销毁量',
                 market != null ? formatCompact(market.blackHoleAmount) : null,
                 _red,
                 isLoading,