feat: forum rich-text editor, emoji picker, mentions, discover nav, feed, uploads, profile

Forum:
- TipTap WYSIWYG editor with full toolbar
- @emoji-mart/react emoji picker (consistent with tweets)
- @mention autocomplete with user search API
- Fix PHP 8.4 parse errors in Blade templates
- Fix thread data display (paginator items)
- Align forum page widths to max-w-5xl

Discover:
- Extract shared _nav.blade.php partial
- Add missing nav links to for-you page
- Add Following link for authenticated users

Feed/Posts:
- Post model, controllers, policies, migrations
- Feed page components (PostComposer, FeedCard, etc)
- Post reactions, comments, saves, reports, sharing
- Scheduled publishing support
- Link preview controller

Profile:
- Profile page components (ProfileHero, ProfileTabs)
- Profile API controller

Uploads:
- Upload wizard enhancements
- Scheduled publish picker
- Studio status bar and readiness checklist

resources/js/components/messaging/MessageBubble.jsx

@@ -151,7 +151,7 @@ export default function MessageBubble({ message, isMine, showAvatar, onReact, on
                       unwrapDisallowed
                       components={{
                         a: ({ href, children }) => (
-                          <a href={href} target="_blank" rel="noopener noreferrer"
+                          <a href={href} target="_blank" rel="noopener noreferrer nofollow"
                             className={isMine ? 'text-blue-200 underline' : 'text-blue-600 dark:text-blue-400 underline'}>
                             {children}
                           </a>