fix(mining): perSecondEarning只在挖矿激活时返回非零值

- GetMiningAccountQuery 检查 config.isActive 状态
- 挖矿未激活时 perSecondEarning 返回 0
- 前端资产页面定时器会因此停止增长

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

backend/services/mining-service/src/application/queries/get-mining-account.query.ts

@@ -51,6 +51,7 @@ export class GetMiningAccountQuery {
     }
 
     // 计算每秒收益 = (用户贡献 / 全网贡献) × 每秒分配量
+    // 只有在挖矿系统激活时才返回非零值
     let perSecondEarning = '0';
     try {
       const [config, totalContribution] = await Promise.all([
@@ -58,7 +59,8 @@ export class GetMiningAccountQuery {
         this.accountRepository.getTotalContribution(),
       ]);
 
-      if (config && totalContribution.value.toNumber() > 0) {
+      // 检查挖矿系统是否激活
+      if (config && config.isActive && totalContribution.value.toNumber() > 0) {
         const userContribution = account.totalContribution.value.toNumber();
         const secondDistribution = config.secondDistribution.value.toNumber();
         const ratio = userContribution / totalContribution.value.toNumber();