fix: 修复 Mall API 数据提取逻辑和添加配置字段

## 问题 1: Settings 缺少 Mall API 配置
**错误**: `'Settings' object has no attribute 'mall_api_url'`

**原因**: Settings 类只有 hyperf 配置，缺少 Mall API 相关字段

**解决方案**: 添加 Mall API 配置字段（第 20-25 行）
```python
mall_api_url: str
mall_tenant_id: str = "2"
mall_currency_code: str = "EUR"
mall_language_id: str = "1"
mall_source: str = "us.qa1.gaia888.com"
```

## 问题 2: Mall API 数据结构解析错误
**现象**: 商品搜索始终返回 0 个商品

**原因**: Mall API 返回的数据结构与预期不符

**Mall API 实际返回**:
```json
{
  "total": 0,
  "data": {
    "data": [],  // ← 商品列表在这里
    "isClothesClassification": false,
    "ad": {...}
  }
}
```

**代码原来查找**: `result.get("list", [])` ❌

**修复后查找**: `result["data"]["data"]` ✅

**解决方案**: 修改数据提取逻辑（第 317-323 行）
```python
if "data" in result and isinstance(result["data"], dict):
    products = result["data"].get("data", [])
else:
    products = result.get("list", [])  # 向后兼容
total = result.get("total", 0)
```

## 调试增强
添加 print 调试语句：
- 第 292 行：打印调用参数
- 第 315 行：打印 Mall API 返回结果

便于诊断 API 调用问题。

## 测试结果

修复前：
```
'Settings' object has no attribute 'mall_api_url'
```

修复后：
```json
{
  "success": true,
  "products": [],
  "total": 0,
  "keyword": "61607"
}
```

✅ 工具调用成功
⚠️ 返回 0 商品（可能是关键词无匹配）

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

mcp_servers/product_mcp/server.py

@@ -17,6 +17,11 @@ class Settings(BaseSettings):
     """Server configuration"""
     hyperf_api_url: str
     hyperf_api_token: str
+    mall_api_url: str
+    mall_tenant_id: str = "2"
+    mall_currency_code: str = "EUR"
+    mall_language_id: str = "1"
+    mall_source: str = "us.qa1.gaia888.com"
     log_level: str = "INFO"
 
     model_config = ConfigDict(env_file=".env")
@@ -277,6 +282,14 @@ async def search_products(
 
     try:
         from shared.mall_client import MallClient
+        import logging
+        logger = logging.getLogger(__name__)
+
+        logger.info(
+            f"search_products called with keyword={keyword}, "
+            f"user_token_prefix={user_token[:20] if user_token else None}..."
+        )
+        print(f"[DEBUG] search_products called: keyword={keyword}, user_token={user_token[:20] if user_token else None}...")
 
         # 使用用户 token 创建 Mall 客户端
         mall = MallClient(
@@ -294,8 +307,19 @@ async def search_products(
             page=page
         )
 
+        logger.info(
+            f"Mall API returned: result_type={type(result).__name__}, "
+            f"result_keys={list(result.keys()) if isinstance(result, dict) else 'not a dict'}, "
+            f"result={result}"
+        )
+        print(f"[DEBUG] Mall API returned: {result}")
+
         # 解析返回结果
-        products = result.get("list", [])
+        # Mall API 返回结构: {"total": X, "data": {"data": [...], ...}}
+        if "data" in result and isinstance(result["data"], dict):
+            products = result["data"].get("data", [])
+        else:
+            products = result.get("list", [])
         total = result.get("total", 0)
 
         # 格式化商品数据