feat(backend): RBAC admin roles + runtime logs service

backend/app/schemas/role.py

@@ -80,12 +80,14 @@ class RoleAssignRequest(BaseModel):
     """角色分配请求 Schema。
 
     Attributes:
-        employee_id: 企微 UserID
+        target: 员工账号或姓名（自动解析为企微 UserID 并校验组织内存在性）【推荐】
+        employee_id: 兼容旧字段，直接传企微 UserID
         role_name: 角色标识（user/agent/admin）
         reason: 分配原因（可选）
     """
 
-    employee_id: str = Field(..., min_length=1, max_length=100, description="企微 UserID")
+    target: Optional[str] = Field(None, min_length=1, max_length=100, description="员工账号或姓名（自动解析）")
+    employee_id: Optional[str] = Field(None, min_length=1, max_length=100, description="兼容字段：企微 UserID")
     role_name: str = Field(..., min_length=1, max_length=50, description="角色标识")
     reason: Optional[str] = Field(None, max_length=500, description="分配原因")