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

app/Http/Controllers/Web/Posts/SearchFeedController.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace App\Http\Controllers\Web\Posts;
+
+use App\Http\Controllers\Controller;
+use App\Services\Posts\PostHashtagService;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Cache;
+use Inertia\Inertia;
+use Inertia\Response;
+
+class SearchFeedController extends Controller
+{
+    public function __construct(private PostHashtagService $hashtagService) {}
+
+    /** GET /feed/search */
+    public function index(Request $request): Response
+    {
+        $trendingHashtags = Cache::remember(
+            'trending_hashtags',
+            300,
+            fn () => $this->hashtagService->trending(10, 24)
+        );
+
+        return Inertia::render('Feed/SearchFeed', [
+            'auth' => $request->user() ? [
+                'user' => [
+                    'id'       => $request->user()->id,
+                    'username' => $request->user()->username,
+                    'name'     => $request->user()->name,
+                    'avatar'   => $request->user()->profile?->avatar_url ?? null,
+                ],
+            ] : null,
+            'initialQuery'    => $request->query('q', ''),
+            'trendingHashtags' => $trendingHashtags,
+        ]);
+    }
+}