dsh-any-attachment: DeepSeek Harness Plugin for Attaching Any File Type via the Web UI

`dsh-any-attachment` is a Web UI plugin for DeepSeek Harness designed to address the issue of agents directly reading files. Users can upload files by drag-and-drop or using the `@` symbol. The system stores them in private directories and inserts pathless `@-mentions` into the message draft. After sending, the agent can read file contents directly through tools, without users needing to download files manually. The plugin also supports image processing and enforces a 25 MB file size limit and a limit on the number of files displayed in the list, helping ensure a clean and secure working environment.