DeepSeek Harness PWA Plugin: Adding Offline and Installation Capabilities

The `dsh-pwa-plugin` for DeepSeek Harness (DSH) is a plugin that enables offline access and desktop installation for applications through a Service Worker. Users need to add the dependency in a DSH Web Profile, register the plugin, and restart the service. The plugin hosts the Service Worker script and manifest, applies differentiated caching strategies (such as Cache-first) to static resources like HTML and JS/CSS, but does not cache API requests. It supports automatic update detection, requires an HTTPS environment, and depends on Cordis version 4.0.1 or higher.