fix(contribution-service): 统一使用api/v2前缀

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

backend/api-gateway/kong.yml

@@ -277,10 +277,9 @@ services:
 
   # ---------------------------------------------------------------------------
   # Contribution Service 2.0 - 算力服务
-  # 服务使用 /api/v1/contributions 前缀
   # ---------------------------------------------------------------------------
   - name: contribution-service-v2
-    url: http://192.168.1.111:3020/api/v1/contributions
+    url: http://192.168.1.111:3020/api/v2/contributions
     routes:
       - name: contribution-v2-api
         paths:

backend/services/contribution-service/src/main.ts

@@ -9,7 +9,7 @@ async function bootstrap() {
   const app = await NestFactory.create(AppModule);
 
   // Global prefix
-  app.setGlobalPrefix('api/v1');
+  app.setGlobalPrefix('api/v2');
 
   // Validation
   app.useGlobalPipes(