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/Services/Posts/PostCountersService.php

@@ -0,0 +1,68 @@
+<?php
+
+namespace App\Services\Posts;
+
+use App\Models\Post;
+use App\Models\PostComment;
+use App\Models\PostReaction;
+use Illuminate\Support\Facades\DB;
+
+/**
+ * Maintains cached counter columns on the posts table.
+ * Called from controllers when reactions/comments are created or deleted.
+ */
+class PostCountersService
+{
+    public function incrementReactions(Post $post): void
+    {
+        $post->increment('reactions_count');
+    }
+
+    public function decrementReactions(Post $post): void
+    {
+        DB::table('posts')
+            ->where('id', $post->id)
+            ->where('reactions_count', '>', 0)
+            ->decrement('reactions_count');
+    }
+
+    public function incrementComments(Post $post): void
+    {
+        $post->increment('comments_count');
+    }
+
+    public function decrementComments(Post $post): void
+    {
+        DB::table('posts')
+            ->where('id', $post->id)
+            ->where('comments_count', '>', 0)
+            ->decrement('comments_count');
+    }
+
+    /**
+     * Recompute both counters from scratch (repair tool).
+     */
+    public function recompute(Post $post): void
+    {
+        Post::withoutTimestamps(function () use ($post) {
+            $post->update([
+                'reactions_count' => PostReaction::where('post_id', $post->id)->count(),
+                'comments_count'  => PostComment::where('post_id', $post->id)->whereNull('deleted_at')->count(),
+                'saves_count'     => \App\Models\PostSave::where('post_id', $post->id)->count(),
+            ]);
+        });
+    }
+
+    public function incrementSaves(Post $post): void
+    {
+        $post->increment('saves_count');
+    }
+
+    public function decrementSaves(Post $post): void
+    {
+        DB::table('posts')
+            ->where('id', $post->id)
+            ->where('saves_count', '>', 0)
+            ->decrement('saves_count');
+    }
+}