dsh-netguard: Egress Policies and Host Allowlist Plugin for DeepSeek Harness

`dsh-netguard` is a plugin for DeepSeek Harness (DSH) that addresses shortcomings in its sandbox mechanism for controlling network traffic. The plugin provides hostname checks, parameter pre-checks, and audit logging, operating in audit-only mode by default. During installation, ensure Harness version compatibility and explicitly enable `fetchProvider` in the configuration. When deploying it, an audit-before-enforcement approach is recommended; however, note that it cannot detect URLs passed through variables and cannot fully prevent data leakage via proxy channels.