fix: display gender in Chinese for avatar list API

Use str(a.gender) instead of a.gender.value to return Chinese
"男"/"女" instead of English "male"/"female" in the avatar_list
endpoint, consistent with other APIs that use get_structured_info().

src/server/main.py

@@ -936,7 +936,7 @@ def get_avatar_list_simple():
             "name": a.name,
             "sect_name": sect_name,
             "realm": realm_str,
-            "gender": a.gender.value,
+            "gender": str(a.gender),
             "age": a.age.age
         })