dsh-ev-range: Electric Vehicle Range Estimation

`dsh-ev-range` is an EV range estimation plugin designed for DeepSeek Harness (DSH). It follows the “everything is a plugin” philosophy, providing a localized pure Node.js implementation that can run without internet access. After executing the installation command, developers can directly invoke the `ev_range` tool in a session to perform precise calculations. This plugin is suitable for development scenarios that require integrating local logic in the DSH environment with minimal network dependency.