dsh-restart: Adding Controlled Restart and Recovery Entry Points for DSH

dsh-restart is a plugin designed to restart the DeepSeek Harness (DSH) process, addressing the issue of needing to manually restart the process and refresh the page after configuration changes. This plugin offers a model tool `restart_harness`, a slash command `/restart`, a settings configuration card, and an "Immediate Restart" button. It also supports configuring automatic continuation prompts after restart and an optional watchdog feature for automatic recovery. Its core features include: 1. **Multiple Restart Methods**: Supports native Node.js restart, with an optional legacy method using PowerShell/WMI/taskkill (disabled by default). 2. **Security**: The restart interface only accepts same-origin requests from the loopback address (127.0.0.1/localhost), rejecting remote or reverse connections.