dsh-ui-background: DeepSeek Harness Web GUI Background Switching Plugin

The DeepSeek Harness (DSH) plugin `dsh-ui-background` provides lightweight background customization for the web interface without modifying the core and with support for persistence. It offers multiple presets, local/Bing wallpaper uploads, and adjustable opacity, blur, and particle light-flow effects. Installation requires the CLI and a restart; uninstalling restores the defaults. Note that the image size limit is 50 MiB.