feat: replace all primary (blue) with contextual colors across entire theme

Eliminate monotonous blue by replacing ~290 primary- references in 60 files
with semantically appropriate colors:

- accent (teal): links, CTAs, buttons, tabs, focus rings, spinners
- purple: Funkwhale/music, photos, Mastodon/fediverse
- surface (neutral): GitHub, dates/metadata, info boxes
- amber: bookmarks, blogroll categories
- red: likes
- green: reposts
- sky: replies
- orange: RSS/feeds, podcasts
- #0085ff: Bluesky brand
- #a730b8: Mastodon brand

Also updates prose link colors in tailwind.config.js, pagefind UI
primary color to teal, and client-side JS color references.

Confab-Link: http://localhost:8080/sessions/bd3f7012-c703-47e9-bfe2-2ad04ce1842d

bookmarks.njk

@@ -29,7 +29,7 @@ permalink: "bookmarks/{% if pagination.pageNumber > 0 %}page/{{ pagination.pageN
       <div class="post-header">
         {% if post.data.title %}
         <h2 class="text-xl font-semibold mb-1 flex-1">
-          <a class="p-name u-url text-surface-900 dark:text-surface-100 hover:text-primary-600 dark:hover:text-primary-400" href="{{ post.url }}">
+          <a class="p-name u-url text-surface-900 dark:text-surface-100 hover:text-amber-600 dark:hover:text-amber-400" href="{{ post.url }}">
             {{ post.data.title }}
           </a>
         </h2>