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

database/migrations/2026_03_02_000001_create_posts_table.php

@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('posts', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('user_id')->constrained()->cascadeOnDelete();
+            $table->string('type', 32)->default('text');   // text | artwork_share | upload | achievement
+            $table->string('visibility', 16)->default('public'); // public | followers | private
+            $table->longText('body')->nullable();
+            $table->json('meta')->nullable();
+            $table->unsignedInteger('reactions_count')->default(0);
+            $table->unsignedInteger('comments_count')->default(0);
+            $table->timestamps();
+            $table->softDeletes();
+
+            $table->index(['user_id', 'created_at']);
+            $table->index(['type', 'created_at']);
+            $table->index(['visibility', 'created_at']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('posts');
+    }
+};