fix(mining-admin): 解包mining-service响应信封，取response.data.data

mining-service返回 { success, data: { ... } } 格式，
mining-admin-service需要取 .data.data 而非 .data，
否则前端读到的是信封对象而非实际数据，导致 TypeError。

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

backend/services/mining-admin-service/src/application/services/system-accounts.service.ts

@@ -47,7 +47,8 @@ export class SystemAccountsService {
       );
 
       const miningDataMap = new Map<string, MiningServiceSystemAccount>();
-      for (const account of response.data.accounts) {
+      const body = response.data?.data ?? response.data;
+      for (const account of body.accounts) {
         // 使用 accountType:regionCode 作为 key，与 contribution 表一致
         const key = account.regionCode
           ? `${account.accountType}:${account.regionCode}`
@@ -321,7 +322,7 @@ export class SystemAccountsService {
         ),
       );
 
-      return response.data;
+      return response.data?.data ?? response.data;
     } catch (error) {
       this.logger.warn(
         `Failed to fetch system account mining records: ${error.message}`,
@@ -365,7 +366,7 @@ export class SystemAccountsService {
         ),
       );
 
-      return response.data;
+      return response.data?.data ?? response.data;
     } catch (error) {
       this.logger.warn(
         `Failed to fetch system account transactions: ${error.message}`,