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

app/Http/Middleware/HandleInertiaRequests.php

@@ -20,6 +20,29 @@ final class HandleInertiaRequests extends Middleware
             return 'studio';
         }
 
+        // Profile pages: /@{username}
+        if (str_starts_with($request->path(), '@')) {
+            return 'profile.show';
+        }
+
+        // Feed pages — ordered most-specific first
+        if ($request->path() === 'feed/trending') {
+            return 'feed.trending';
+        }
+
+        if ($request->path() === 'feed/saved') {
+            return 'feed.saved';
+        }
+
+        if (str_starts_with($request->path(), 'feed')) {
+            return 'feed.following';
+        }
+
+        // Hashtag pages: /tags/{tag}
+        if (str_starts_with($request->path(), 'tags/')) {
+            return 'feed.hashtag';
+        }
+
         return $this->rootView;
     }