dsh-plugin-offpeak-badge: DeepSeek API Peak/Off-Peak Billing Status Indicator

`dsh-plugin-offpeak-badge` is a plugin designed for DeepSeek Harness (DSH) that addresses the issue of users being unable to easily confirm API billing periods (off-peak or peak). The plugin displays a color-coded status badge in the sidebar brand row, with hover details showing the current rule, date, and switch time. It includes a holiday calendar and supports accessibility. Developers can install it via the command line or a GUI, helping control costs and avoid unnecessary expenses during off-work hours.