dsh-webui-auth: Adding Persistent Login Access Control to DSH WebUI

dsh-webui-auth is the authentication plugin for DeepSeek Harness (DSH) WebUI, licensed under MIT and with zero dependencies. This plugin wraps core routes at runtime, providing four layers of protection for WebUI resources, API endpoints, and WebSocket connections without modifying the DSH source code, forcing unauthenticated users to log in. Its core features include: storing passwords with scrypt hashing, session persistence in sessions.jsonl maintained by HttpOnly cookies; implementing login rate limiting (5 attempts per minute per IP) and security header configuration; recording pseudonymized audit logs; supporting Setup Token initialization on first startup. Passwords can be reset by deleting the credential file if forgotten. Installation is done via npm.