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

js/webmentions.js

@@ -241,7 +241,7 @@
       const published = item.published || item['wm-received'];
 
       const li = document.createElement('li');
-      li.className = 'p-4 bg-surface-100 dark:bg-surface-800 rounded-lg ring-2 ring-primary-500';
+      li.className = 'p-4 bg-surface-100 dark:bg-surface-800 rounded-lg ring-2 ring-accent-500';
       li.dataset.new = 'true';
 
       // Build reply card using DOM methods
@@ -288,7 +288,7 @@
       dateLink.appendChild(timeEl);
 
       const newBadge = document.createElement('span');
-      newBadge.className = 'text-xs text-primary-600 dark:text-primary-400 font-medium';
+      newBadge.className = 'text-xs text-accent-600 dark:text-accent-400 font-medium';
       newBadge.textContent = 'NEW';
 
       headerDiv.appendChild(authorLink);
@@ -339,13 +339,13 @@
 
       const link = document.createElement('a');
       link.href = item.url || '#';
-      link.className = 'text-primary-600 dark:text-primary-400 hover:underline';
+      link.className = 'text-accent-600 dark:text-accent-400 hover:underline';
       link.target = '_blank';
       link.rel = 'noopener';
       link.textContent = `${author.name || 'Someone'} mentioned this on ${formatDate(published)}`;
 
       const badge = document.createElement('span');
-      badge.className = 'text-xs text-primary-600 dark:text-primary-400 font-medium ml-1';
+      badge.className = 'text-xs text-accent-600 dark:text-accent-400 font-medium ml-1';
       badge.textContent = 'NEW';
 
       li.appendChild(link);