refactor: remove Vibrant.js (#1236)

* refactor: migrate image color extraction from client-side JavaScript to server-side Hugo.

* fix: check if image exists before accessing .Resource

layouts/_partials/article-list/tile.html

@@ -8,7 +8,16 @@
         </div>
         {{ end }}
 
-        <div class="article-details">
+        <div class="article-details"
+            {{- if and $image $image.Resource -}}
+                {{- $colors := $image.Resource.Colors -}}
+                {{- if $colors -}}
+                    {{- $vibrant := index $colors 0 -}}
+                    {{- $darkMuted := index $colors 1 | default $vibrant -}}
+                    style="background: linear-gradient(0deg, {{ $darkMuted }}80 0%, {{ $vibrant }}C0 100%);"
+                {{- end -}}
+            {{- end -}}
+        >
             <h2 class="article-title">
                 {{- .context.Title -}}
             </h2>