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

notes.njk

@@ -28,7 +28,7 @@ permalink: "notes/{% if pagination.pageNumber > 0 %}page/{{ pagination.pageNumbe
     <li class="h-entry post-card border-l-[3px] border-l-surface-300 dark:border-l-surface-600">
       <div class="post-header">
         <a class="u-url" href="{{ post.url }}">
-          <time class="dt-published text-sm text-primary-600 dark:text-primary-400 font-medium" datetime="{{ post.date | isoDate }}">
+          <time class="dt-published text-sm text-surface-500 dark:text-surface-400 font-medium" datetime="{{ post.date | isoDate }}">
             {{ post.date | dateDisplay }}
           </time>
         </a>
@@ -48,7 +48,7 @@ permalink: "notes/{% if pagination.pageNumber > 0 %}page/{{ pagination.pageNumbe
         {{ post.templateContent | safe }}
       </div>
       <div class="post-footer mt-3">
-        <a href="{{ post.url }}" class="text-sm text-primary-600 dark:text-primary-400 hover:underline">
+        <a href="{{ post.url }}" class="text-sm text-accent-600 dark:text-accent-400 hover:underline">
           Permalink
         </a>
       </div>