docs: polish repository presentation

Add a compact centered banner and documentation link to the top of the
README, add the site logo and a favicon (generated from the logo) to the
MkDocs Material theme, and commit the generated visual assets.

docs/ untouched.

Author: fnayou

README.md

@@ -1,14 +1,20 @@
 # dotfiles
 
+<p align="center">
+  <img src="website/assets/images/dotfiles-readme-banner.png" alt="fnayou/dotfiles banner" />
+</p>
+
+<p align="center">
+  <a href="https://fnayou.github.io/dotfiles/">Documentation</a>
+</p>
+
 Private, safe, cross-platform personal dotfiles for **macOS** and **EndeavourOS / Arch Linux**,
 managed with [GNU Stow](https://www.gnu.org/software/stow/).
 
 macOS is the primary environment; Arch is supported from the start. Configs are version-controlled
 in `stow/common/` and only ever symlinked into `$HOME` by a **deliberate, manual** Stow step —
 never automatically.
 
-📖 **Documentation site:** <https://fnayou.github.io/dotfiles/>
-
 ## Status
 
 ```

mkdocs.yml

@@ -8,6 +8,8 @@ docs_dir: website
 
 theme:
   name: material
+  logo: assets/images/dotfiles-logo.png
+  favicon: assets/images/favicon.png
   palette:
     scheme: slate
     primary: blue