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/uploads/UploadWizard.jsx

@@ -606,7 +606,7 @@ export default function UploadWizard({
           <div className="grid grid-cols-1 gap-3 text-sm text-white/80 md:grid-cols-2">
             <div><span className="text-white/50">Upload ID:</span> {uploadId || '—'}</div>
             <div><span className="text-white/50">Title:</span> {details.title || '—'}</div>
-            <div className="md:col-span-2"><span className="text-white/50">URL preview:</span> /artwork/{urlPreviewSlug}</div>
+            <div className="md:col-span-2"><span className="text-white/50">URL preview:</span> /art/{urlPreviewSlug}</div>
             <div><span className="text-white/50">Category:</span> {details.category_id || '—'}</div>
             <div><span className="text-white/50">Tags:</span> {(details.tags || []).join(', ') || '—'}</div>
             <div className="md:col-span-2"><span className="text-white/50">Preview path:</span> {previewPath || 'Will be resolved by backend pipeline'}</div>