dsh-prompt-optimize: Prompt Optimization, Personalized Instructions, and Usage Cards for DSH Web

`dsh-prompt-optimize` is a DSH web plugin designed to address the issues of scattered functionalities in draft rewriting, long-term preference settings, long conversation navigation, and API usage viewing. The plugin offers four core features: firstly, prompt optimization, which utilizes the DeepSeek model to rewrite drafts with a preview-before-apply option; secondly, personalized custom instructions, allowing users to set and persistently save long-term preferences; thirdly, user question anchors, enabling quick navigation and scrolling to specific user messages in long conversations via anchors on the right side or top; and fourthly, a DeepSeek API floating usage card, which displays real-time spending and balance for the current key over today, yesterday, and the last seven days, with data calculated in GMT+8. The plugin is licensed under MIT, requires the DSH environment to operate, and supports installation and uninstallation via the `dsh plugin` command.