docs(releaser): add logo to documentation site and README

- docs/hugo.toml: set geekdocLogo to images/releaser-logo-1024.png so
  Geekdoc renders it in the site header
- docs/static/images/releaser-logo-128.png: 128×128 version resized from
  the 1024×1024 source via ImageMagick for README display
- README.md: add logo above the release badge
- .gitignore: scope releaser-* to repo root (/releaser-*) so it no
  longer matches files inside docs/static/images/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/hugo.toml

@@ -13,6 +13,7 @@ pygmentsCodeFences = true
     endLevel = 9
 
 [params]
+  geekdocLogo = "images/releaser-logo-1024.png"
   geekdocRepo = "https://git.k3nny.fr/releaser"
   geekdocEditPath = "edit/main/docs/content"
   geekdocSearch = true