dsh-llm-providers-ui: DeepSeek Harness Shared LLM Providers Settings Shell

`dsh-llm-providers-ui` is the core plugin of DeepSeek Harness (DSH), designed to centrally manage LLM Provider settings pages. It provides core features such as a settings shell, card sorting, quota dashboards, and model catalog editing, reducing management complexity in multi-provider environments. As a host plugin, it must be added before installing other Provider plugins and must adhere to its specific version dependencies, export paths, and installation contract.