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/forum/Breadcrumbs.jsx

@@ -0,0 +1,30 @@
+import React from 'react'
+
+export default function Breadcrumbs({ items = [] }) {
+  return (
+    <nav className="text-sm text-zinc-400" aria-label="Breadcrumb">
+      <ol className="flex flex-wrap items-center gap-1.5">
+        {items.map((item, i) => (
+          <React.Fragment key={i}>
+            {i > 0 && (
+              <li aria-hidden="true" className="text-zinc-600">
+                <svg width="16" height="16" viewBox="0 0 16 16" fill="none" className="inline-block">
+                  <path d="M6 4l4 4-4 4" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round" />
+                </svg>
+              </li>
+            )}
+            <li>
+              {item.href ? (
+                <a href={item.href} className="hover:text-zinc-200 transition-colors">
+                  {item.label}
+                </a>
+              ) : (
+                <span className="text-zinc-200">{item.label}</span>
+              )}
+            </li>
+          </React.Fragment>
+        ))}
+      </ol>
+    </nav>
+  )
+}