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

about.njk

@@ -17,7 +17,7 @@ eleventyExcludeFromCollections: true
         {{ site.author.name }}
       </h1>
       {% if site.author.title %}
-      <p class="p-job-title text-xl text-primary-600 dark:text-primary-400 mb-2">
+      <p class="p-job-title text-xl text-accent-600 dark:text-accent-400 mb-2">
         {{ site.author.title }}
       </p>
       {% endif %}