dsh-network-config: DeepSeek Harness Network Proxy Configuration Plugin

The DeepSeek Harness Network Configuration plugin addresses the limitations of relying on environment variables and requiring restarts. It supports system proxy, direct connection, and custom proxy modes, with built-in rules to automatically bypass loopback and private IP addresses. Users can switch modes instantly via the application interface or API without restarting. Installation requires a PowerShell environment, while uninstallation requires restarting the application. Note: Only HTTP(S) proxies are supported; SOCKS and PAC scripts are not currently supported.