dsh-theme-customizer: Custom Theme Plugin for the DeepSeek Harness Web Interface

The DeepSeek Harness (DSH) theme customization plugin, developed by lxxz1918, provides a visual web-based configuration solution. It supports comprehensive customization of backgrounds (including image cropping), colors, fonts, and borders across seven areas, such as the main interface, sidebar, and chat area, and also supports local persistence as well as importing and exporting presets in `.tczp` format. Users can make quick adjustments through the settings panel or floating window, with changes taking effect immediately. Restart DSH Web after installation. To use the persistent Cordis button feature, run the accompanying patch script.