fix(mining-admin-service): add logging and fix null data handling in getMiningStatus

- Add debug logging to trace mining service calls
- Return error object instead of null when data is missing
- Include error message in response for debugging

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

backend/services/mining-admin-service/src/api/controllers/config.controller.ts

@@ -63,20 +63,30 @@ export class ConfigController {
   @ApiOperation({ summary: '获取挖矿状态' })
   async getMiningStatus() {
     const miningServiceUrl = this.appConfigService.get<string>('MINING_SERVICE_URL', 'http://localhost:3021');
+    this.logger.log(`Fetching mining status from ${miningServiceUrl}/api/v2/admin/status`);
     try {
       const response = await fetch(`${miningServiceUrl}/api/v2/admin/status`);
       if (!response.ok) {
-        throw new Error('Failed to fetch mining status');
+        throw new Error(`Failed to fetch mining status: ${response.status}`);
       }
       const result = await response.json();
+      this.logger.log(`Mining service response: ${JSON.stringify(result)}`);
       // mining-service 返回 { success, data, timestamp }，需要解包 data
-      return result.data || result;
+      if (result.data) {
+        return result.data;
+      }
+      // 如果没有 data 字段，返回错误状态
+      return {
+        initialized: false,
+        isActive: false,
+        error: 'Invalid response from mining service',
+      };
     } catch (error) {
       this.logger.error('Failed to get mining status', error);
       return {
         initialized: false,
         isActive: false,
-        error: 'Unable to connect to mining service',
+        error: `Unable to connect to mining service: ${error.message}`,
       };
     }
   }