Update site content, styling, and review layout

Revise about page, hello world post, and The Compound review. Add book
cover support to review template, favicon, typographer config, and
cover image enrichment script.

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

site/layouts/reviews/single.html

@@ -17,8 +17,13 @@
       <span class="rating-blocks">{{- strings.Repeat $rating "▓" -}}{{- strings.Repeat (sub 5 $rating) "░" -}}</span>
       <span class="rating-num">{{ $rating }}/5</span>
     </span>
+
   </div>
 
+  {{ with .Params.cover }}
+  <img class="book-cover" src="{{ . }}" alt="Cover of {{ $.Title }}">
+  {{ end }}
+
   {{ .Content }}
 
   {{ with .Params.tags }}