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/Pages/Forum/ForumIndex.jsx

@@ -0,0 +1,31 @@
+import React from 'react'
+import CategoryCard from '../../components/forum/CategoryCard'
+
+export default function ForumIndex({ categories = [] }) {
+  return (
+    <div className="px-4 pt-10 pb-20 sm:px-6 lg:px-8 max-w-5xl mx-auto">
+      {/* Header */}
+      <div className="mb-8">
+        <p className="text-xs font-semibold uppercase tracking-widest text-white/30 mb-1">Community</p>
+        <h1 className="text-3xl font-bold text-white leading-tight">Forum</h1>
+        <p className="mt-1.5 text-sm text-white/50">Browse forum sections and join the conversation.</p>
+      </div>
+
+      {/* Category grid */}
+      {categories.length === 0 ? (
+        <div className="rounded-2xl border border-white/[0.06] bg-nova-800/50 p-12 text-center">
+          <svg className="mx-auto mb-4 text-zinc-600" width="48" height="48" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round">
+            <path d="M21 15a2 2 0 01-2 2H7l-4 4V5a2 2 0 012-2h14a2 2 0 012 2z" />
+          </svg>
+          <p className="text-sm text-zinc-500">No forum categories available yet.</p>
+        </div>
+      ) : (
+        <div className="grid grid-cols-1 gap-5 sm:grid-cols-2">
+          {categories.map((cat) => (
+            <CategoryCard key={cat.id ?? cat.slug} category={cat} />
+          ))}
+        </div>
+      )}
+    </div>
+  )
+}