ui: unify logo across themes and update favicon

templates/components/footer.gohtml

@@ -2,10 +2,7 @@
 <footer class="mt-auto border-t border-neutral-800 bg-background-sidebar py-8 px-6 md:px-12">
   <div class="flex flex-col items-center justify-between gap-6 sm:flex-row">
     <div class="flex items-center gap-3">
-      <picture>
-        <source media="(prefers-color-scheme: dark)" srcset="/static/readme-logo-dark.svg" />
-        <img src="/static/readme-logo-light.svg" alt="MAL" class="h-6 w-6" />
-      </picture>
+      <img src="/static/readme-logo-light.svg" alt="MAL" class="h-6 w-6" />
       <span class="text-neutral-300 font-semibold text-lg tracking-tight">MyAnimeList</span>
     </div>
     <div class="flex items-center gap-6">