DSH Plugin dsh-deepseek-billing: Sidebar Display of DeepSeek Balance and Session Cost Estimation

`dsh-deepseek-billing` is a DSH WebUI community plugin (v0.1.0-rc.8, MIT license) designed to address the pain point of developers frequently querying DeepSeek account balance and costs when running model tasks. This plugin displays the DeepSeek account balance persistently in the left sidebar of the DSH web interface and estimates the current session cost in real time. Core features include: 1. **Balance Display**: Directly calls the official DeepSeek API, reuses the API key from the current session, auto-refreshes every 60 seconds, and also supports manual refresh. 2. **Cost Estimation**: Prices and accumulates each successful assistant reply individually, showing recharged/gifted balance, token details, cache hit rate, and input/output cost subtotals. The cost is an estimate and is for reference only.