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/MentionList.jsx

@@ -0,0 +1,76 @@
+import React, { forwardRef, useEffect, useImperativeHandle, useState } from 'react'
+
+/**
+ * Dropdown list rendered by TipTap's mention suggestion.
+ * Receives `items` (user objects) and keyboard nav commands via ref.
+ */
+const MentionList = forwardRef(function MentionList({ items, command }, ref) {
+  const [selectedIndex, setSelectedIndex] = useState(0)
+
+  // Reset selection when items change
+  useEffect(() => setSelectedIndex(0), [items])
+
+  // Expose keyboard handler to TipTap suggestion plugin
+  useImperativeHandle(ref, () => ({
+    onKeyDown: ({ event }) => {
+      if (event.key === 'ArrowUp') {
+        setSelectedIndex((i) => (i + items.length - 1) % items.length)
+        return true
+      }
+      if (event.key === 'ArrowDown') {
+        setSelectedIndex((i) => (i + 1) % items.length)
+        return true
+      }
+      if (event.key === 'Enter') {
+        selectItem(selectedIndex)
+        return true
+      }
+      return false
+    },
+  }))
+
+  const selectItem = (index) => {
+    const item = items[index]
+    if (item) {
+      command({ id: item.username, label: item.username })
+    }
+  }
+
+  if (!items.length) {
+    return (
+      <div className="rounded-xl border border-white/[0.08] bg-nova-800 p-3 shadow-xl backdrop-blur">
+        <p className="text-xs text-zinc-500">No users found</p>
+      </div>
+    )
+  }
+
+  return (
+    <div className="min-w-[200px] overflow-hidden rounded-xl border border-white/[0.08] bg-nova-800 shadow-xl backdrop-blur">
+      {items.map((item, index) => (
+        <button
+          key={item.id}
+          type="button"
+          onClick={() => selectItem(index)}
+          className={[
+            'flex w-full items-center gap-2.5 px-3 py-2 text-left text-sm transition-colors',
+            index === selectedIndex
+              ? 'bg-sky-600/20 text-white'
+              : 'text-zinc-300 hover:bg-white/[0.04]',
+          ].join(' ')}
+        >
+          <img
+            src={item.avatar_url}
+            alt=""
+            className="h-6 w-6 rounded-full border border-white/10 object-cover"
+          />
+          <span className="truncate font-medium">@{item.username}</span>
+          {item.name && item.name !== item.username && (
+            <span className="truncate text-xs text-zinc-500">{item.name}</span>
+          )}
+        </button>
+      ))}
+    </div>
+  )
+})
+
+export default MentionList