C7/C8: employees.last_login_ip 列补全（ALTER TABLE 迁移）+ redis decode 兼容修复 7 处（wecom_service×2/employee_directory×3/auth_wecom_sso×2，统一 isinstance 保护模式）

backend/app/services/employee_directory.py

@@ -62,7 +62,9 @@ async def get_org_directory(
             raw = await redis.get(ORG_DIRECTORY_CACHE_KEY)
             if raw:
                 logger.debug("命中组织目录缓存")
-                return json.loads(raw.decode("utf-8")), True
+                # v4.0 C8 修复：兼容 str/bytes
+                raw = raw if isinstance(raw, str) else raw.decode("utf-8")
+                return json.loads(raw), True
         except Exception as e:
             logger.warning(f"读取组织目录缓存失败（降级）: {e}")
 
@@ -306,7 +308,9 @@ async def get_cached_dept_list(
         try:
             raw = await redis.get(DEPT_LIST_CACHE_KEY)
             if raw:
-                return json.loads(raw.decode("utf-8"))
+                # v4.0 C8 修复：兼容 str/bytes
+                raw = raw if isinstance(raw, str) else raw.decode("utf-8")
+                return json.loads(raw)
         except Exception as e:
             logger.warning(f"读取部门列表缓存失败: {e}")
 
@@ -607,7 +611,9 @@ async def get_org_tree_cached(
         try:
             raw = await redis.get(cache_key)
             if raw:
-                tree = json.loads(raw.decode("utf-8"))
+                # v4.0 C8 修复：兼容 str/bytes
+                raw = raw if isinstance(raw, str) else raw.decode("utf-8")
+                tree = json.loads(raw)
                 logger.debug(f"命中组织架构树缓存: {endpoint}")
         except Exception as e:
             logger.warning(f"读取组织架构树缓存失败: {e}")