dsh-dify-marketplace: Integrating Dify Marketplace into DeepSeek Harness

The `dsh-dify-marketplace` plugin for DeepSeek Harness (DSH) is designed to integrate the Dify Marketplace into DSH's settings interface. Operating in Host + Web UI mode, it supports plugin browsing, searching, viewing details, and installation, and uses the official daemon to handle package installation and credential management to ensure security. It addresses developers' pain points when managing Dify ecosystem plugins in the DSH environment, requiring specific parameters to be configured and compatible with DSH `v0.1.0-rc.7`.