dsh-outbound-proxy: Configuring a Global Outbound Proxy in DeepSeek Harness

The DeepSeek Harness (DSH) outbound proxy plugin provides a graphical interface that allows users to configure a global proxy in Settings, solving the cumbersome problem of modifying environment variables in restricted network environments. The plugin supports HTTP/HTTPS protocols, and its configuration is persistently written to the `~/.dsh/.env` file while automatically merging with existing content. Installation requires adding the dependency to the web profile and restarting DSH. The plugin takes effect through DSH's built-in HTTP proxy component, so a restart is required after any changes. It follows DSH community ecosystem standards and is suitable for users who need to centrally manage LLM, search, and HTTP MCP traffic.