Branding: logo + social preview (matching the main ComfyPeeper style)

- assets/icon.svg + icon.png: two-node workflow mark with a green "send"
  arrow, on a dark brand-bordered square
- assets/social-preview.svg + social-preview.png (1280×640): mirrors the
  main repo's banner, lens holding a two-way arrow (→ ComfyUI, ← Discord)
- README shows the banner; pyproject Icon points at icon.png

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -1,6 +1,12 @@
-# ComfyPeeper Companion (ComfyUI extension)
+<div align="center">
 
-A small ComfyUI extension that pairs with the **[ComfyPeeper](https://github.com/ethanfel/Discord-ComfyPeeper)**
+![ComfyPeeper Companion](assets/social-preview.png)
+
+# ComfyPeeper Companion
+
+</div>
+
+A small ComfyUI extension that pairs with the **[ComfyPeeper](https://github.com/Ethanfel/Discord-ComfyPeeper)**
 Discord plugin to enable two things plain ComfyUI's API can't:
 
 - **Send to ComfyUI** — ComfyPeeper can load a workflow straight into your **open ComfyUI