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

_includes/components/post-navigation.njk

@@ -14,7 +14,7 @@
       {% set _replyToUrl = _prevPost.data.inReplyTo or _prevPost.data.in_reply_to %}
       {% set _prevOgSlug = _prevPost.url | ogSlug %}
       {% set _prevHasOg = _prevOgSlug | hasOgImage %}
-      <a href="{{ _prevPost.url }}" class="group flex items-start gap-3 text-sm text-primary-600 dark:text-primary-400 hover:underline">
+      <a href="{{ _prevPost.url }}" class="group flex items-start gap-3 text-sm text-accent-600 dark:text-accent-400 hover:underline">
         {% if _prevHasOg %}
         <img src="/og/{{ _prevOgSlug }}.png" alt="" class="w-20 h-[42px] object-cover rounded flex-shrink-0 opacity-80 group-hover:opacity-100 transition-opacity" loading="lazy" eleventy:ignore>
         {% endif %}
@@ -29,7 +29,7 @@
           <svg class="w-3.5 h-3.5 text-green-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 4v5h.582m15.356 2A8.001 8.001 0 004.582 9m0 0H9m11 11v-5h-.581m0 0a8.003 8.003 0 01-15.357-2m15.357 2H15"/></svg>
           Reposted {{ _repostedUrl | replace("https://", "") | truncate(35) }}
           {% elif _replyToUrl %}
-          <svg class="w-3.5 h-3.5 text-primary-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6"/></svg>
+          <svg class="w-3.5 h-3.5 text-accent-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6"/></svg>
           Reply to {{ _replyToUrl | replace("https://", "") | truncate(35) }}
           {% else %}
           {{ _prevPost.data.title or _prevPost.data.name or (_prevPost.templateContent | striptags | truncate(50)) or "Note" }}
@@ -49,7 +49,7 @@
       {% set _replyToUrl = _nextPost.data.inReplyTo or _nextPost.data.in_reply_to %}
       {% set _nextOgSlug = _nextPost.url | ogSlug %}
       {% set _nextHasOg = _nextOgSlug | hasOgImage %}
-      <a href="{{ _nextPost.url }}" class="group flex items-start gap-3 text-sm text-primary-600 dark:text-primary-400 hover:underline {% if _prevPost %}justify-end{% endif %}">
+      <a href="{{ _nextPost.url }}" class="group flex items-start gap-3 text-sm text-accent-600 dark:text-accent-400 hover:underline {% if _prevPost %}justify-end{% endif %}">
         <span class="line-clamp-2 flex items-center gap-1.5 {% if _prevPost %}justify-end{% endif %}">
           {% if _likedUrl %}
           <svg class="w-3.5 h-3.5 text-red-500 flex-shrink-0" fill="currentColor" viewBox="0 0 24 24"><path d="M12 21.35l-1.45-1.32C5.4 15.36 2 12.28 2 8.5 2 5.42 4.42 3 7.5 3c1.74 0 3.41.81 4.5 2.09C13.09 3.81 14.76 3 16.5 3 19.58 3 22 5.42 22 8.5c0 3.78-3.4 6.86-8.55 11.54L12 21.35z"/></svg>
@@ -61,7 +61,7 @@
           <svg class="w-3.5 h-3.5 text-green-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 4v5h.582m15.356 2A8.001 8.001 0 004.582 9m0 0H9m11 11v-5h-.581m0 0a8.003 8.003 0 01-15.357-2m15.357 2H15"/></svg>
           Reposted {{ _repostedUrl | replace("https://", "") | truncate(35) }}
           {% elif _replyToUrl %}
-          <svg class="w-3.5 h-3.5 text-primary-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6"/></svg>
+          <svg class="w-3.5 h-3.5 text-accent-500 flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M3 10h10a8 8 0 018 8v2M3 10l6 6m-6-6l6-6"/></svg>
           Reply to {{ _replyToUrl | replace("https://", "") | truncate(35) }}
           {% else %}
           {{ _nextPost.data.title or _nextPost.data.name or (_nextPost.templateContent | striptags | truncate(50)) or "Note" }}