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/mentionSuggestion.js

@@ -0,0 +1,74 @@
+import { ReactRenderer } from '@tiptap/react'
+import tippy from 'tippy.js'
+import MentionList from './MentionList'
+
+/**
+ * TipTap suggestion configuration for @mentions.
+ * Fetches users from /api/search/users?q=... as the user types.
+ */
+export default {
+  items: async ({ query }) => {
+    if (!query || query.length < 2) return []
+
+    try {
+      const res = await fetch(`/api/search/users?q=${encodeURIComponent(query)}&per_page=6`)
+      if (!res.ok) return []
+      const json = await res.json()
+      return json.data ?? []
+    } catch {
+      return []
+    }
+  },
+
+  render: () => {
+    let component
+    let popup
+
+    return {
+      onStart: (props) => {
+        component = new ReactRenderer(MentionList, {
+          props,
+          editor: props.editor,
+        })
+
+        if (!props.clientRect) return
+
+        popup = tippy('body', {
+          getReferenceClientRect: props.clientRect,
+          appendTo: () => document.body,
+          content: component.element,
+          showOnCreate: true,
+          interactive: true,
+          trigger: 'manual',
+          placement: 'bottom-start',
+          theme: 'mention',
+          arrow: false,
+          offset: [0, 8],
+        })
+      },
+
+      onUpdate: (props) => {
+        component?.updateProps(props)
+
+        if (!props.clientRect) return
+
+        popup?.[0]?.setProps({
+          getReferenceClientRect: props.clientRect,
+        })
+      },
+
+      onKeyDown: (props) => {
+        if (props.event.key === 'Escape') {
+          popup?.[0]?.hide()
+          return true
+        }
+        return component?.ref?.onKeyDown(props) ?? false
+      },
+
+      onExit: () => {
+        popup?.[0]?.destroy()
+        component?.destroy()
+      },
+    }
+  },
+}