dsh-whale-avatar: Add avatars and names to DSH Web UI assistant messages

dsh-whale-avatar is a pure client-side plugin for the DSH Web UI with a single function: adding avatars (the App icon "Blue Fat Fish") and names to assistant messages, solving the issue of distinguishing message sources in long chat histories. It is maintained by lhjlol and hosted on GitHub. The implementation involves injecting a style tag into the page and using a CSS rule via the ::before pseudo-element to render the avatar and name. It does not alter the DOM structure, so the effect persists after React re-rendering, and the styles adapt to the day/night theme. The avatar is a 56px PNG embedded in a 28x28 SVG data URI, ensuring clarity on Retina displays. Installation is available via the Oh-DSH Desktop plugin marketplace.