fix(kong): 修复auth-service路由配置

- 将service URL从 /api/v2 改为根路径
- 设置 strip_path: false 直接透传请求路径
- 保持前后端路径一致: /api/v2/auth/...

问题原因: strip_path: true 会移除 /api/v2/auth，
导致后端收到 /api/v2/login 而不是 /api/v2/auth/login

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

backend/api-gateway/kong.yml

@@ -339,19 +339,20 @@ services:
 
   # ---------------------------------------------------------------------------
   # Auth Service 2.0 - 用户认证服务
-  # 服务全局前缀: /api/v2, 所以需要strip_path后添加前缀
+  # 前端路径: /api/v2/auth/...
+  # 后端路径: /api/v2/auth/... (strip_path: false, 直接透传)
   # ---------------------------------------------------------------------------
   - name: auth-service-v2
-    url: http://192.168.1.111:3024/api/v2
+    url: http://192.168.1.111:3024
     routes:
       - name: auth-v2-api
         paths:
           - /api/v2/auth
-        strip_path: true
+        strip_path: false
       - name: auth-v2-health
         paths:
           - /api/v2/auth/health
-        strip_path: true
+        strip_path: false
 
   # ---------------------------------------------------------------------------
   # Mining Wallet Service 2.0 - 挖矿钱包服务