scaffold

Package httpcodec 把 Mix 网关改成 protobuf 优先、JSON 备选（看 Accept）。

Package httproute 把请求路径收敛成适合做指标标签的路由模板。

Package page 统一分页参数的取值范围。

Package pwd signs and verifies three-segment tokens whose header and body are protobuf messages, using golang-jwt SigningMethod for the signature segment (same HS256/HS384/HS512 crypto as JWT, protobuf wire instead of JSON).