dsh-access-gate: Provides password access for DSH remote /api access

dsh-access-gate is a remote access authentication gateway plugin for DeepSeek Harness (DSH), designed to address security exposure issues when accessing DSH Web via public domain names or LAN IPs. By default, this plugin allows passwordless remote access; once configured with a password, it restricts non-local direct connections and enforces password login, while retaining the native local directory selection experience and promising no residual files upon uninstallation. Core features include: login session management based on HttpOnly Cookies (default validity period of 7 days); secure password comparison using SHA-256 and timingSafeEqual; and replacing dsh-lan-access to provide 0.0.0.0 binding and crypto.randomUUID polyfill.