dsh-simple-auth: DeepSeek Harness Ultra-Lightweight Login Gateway

`dsh-simple-auth` is an ultra-lightweight web plugin for DeepSeek Harness (DSH) intended to replace complex login solutions. It provides access control via shared keys or primary/guest keys, and supports ACL-based session isolation and sharing. It employs a "fail-closed" strategy to ensure security and reliability. Users can install it using the `dsh plugin` command and configure options such as keys and session TTL in `cordis.patch.yml`. After installation, the `DSH_SIMPLE_AUTH_KEY` environment variable must be set and the service restarted. Note that it only handles access control, does not substitute for TLS, and shares real-time agents rather than plain text.