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/views/profile/show.blade.php

@@ -0,0 +1,20 @@
+@extends('layouts.nova')
+
+@push('head')
+    @vite(['resources/js/profile.jsx'])
+    {{-- OG image (not in nova base layout) --}}
+    @if(!empty($og_image))
+        <meta property="og:image" content="{{ $og_image }}">
+    @endif
+    <meta property="og:url" content="{{ $page_canonical ?? url()->current() }}">
+    <style>
+        /* Ensure profile tab bar does not hide behind the main navbar */
+        .profile-tabs-sticky {
+            top: var(--navbar-height, 4rem);
+        }
+    </style>
+@endpush
+
+@section('content')
+    @inertia
+@endsection