DSH-DeepSeek-Quota: Display DeepSeek Quota and Usage in DSH Web Interface

`dsh-deepseek-quota` is an MIT-licensed plugin for the DeepSeek Harness (DSH) web interface, designed to address the inconvenience of quota viewing. It utilizes the `shell.overlay` slot to display a floating card in the bottom-right corner of the page, showing in real time the total balance, availability status, current conversation cost, today's consumption, and gifted/recharged balance. The plugin supports both automatic and manual refresh: the balance updates every 60 seconds, while the current conversation cost updates every 5 seconds. It calculates costs based on DeepSeek's official price list and the peak-valley pricing rules effective from August 17, 2026, and alerts users to peak hours (Beijing time 09:00–12:00 and 14:00–18:00). For today's consumption, if the `DEEPSEEK_PLATFORM` is configured.