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/artwork/ArtworkShareButton.jsx

@@ -20,7 +20,7 @@ function ShareIcon() {
  *   shareUrl – canonical URL to share
  *   size     – 'default' | 'small' (for mobile bar)
  */
-export default function ArtworkShareButton({ artwork, shareUrl, size = 'default' }) {
+export default function ArtworkShareButton({ artwork, shareUrl, size = 'default', isLoggedIn = false }) {
   const [modalOpen, setModalOpen] = useState(false)
 
   const openModal = useCallback(
@@ -69,6 +69,7 @@ export default function ArtworkShareButton({ artwork, shareUrl, size = 'default'
             onClose={closeModal}
             artwork={artwork}
             shareUrl={shareUrl}
+            isLoggedIn={isLoggedIn}
           />
         </Suspense>
       )}