dsh-api-balance: Web Sidebar Balance Widget and Query Tool

The `dsh-api-balance` plugin integrates DeepSeek Harness's API balance monitoring into the web interface, supporting a sidebar widget and model calls. It retrieves balance information via polling or a tool, refreshes every 20 seconds, and includes a caching mechanism. Installation requires Node.js >= 22.19 and supports pnpm or manual setup; configuration requires specifying the API Key environment variable, and changes take effect after a restart.