feat(api): add AI text-to-deck generation, wallet deposit structure, and profile/notification endpoints

Fills the gaps between the admin panel screens and the backend: a full
free-text + slide-count + language -> AI-generated presentation flow with
new slide-cloning logic in TemplateFillService, a "my presentations" list
endpoint, a swappable payment-gateway structure for wallet top-ups (fake
driver for now), and avatar upload / public-profile toggle / account
deletion / password change / notification preference endpoints.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/Models/NotificationPreference.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+#[Fillable([
+    'user_id',
+    'comment_on_presentation',
+    'form_reply',
+    'new_follower',
+    'news_announcements',
+    'weekly_product_updates',
+    'weekly_blog_digest',
+])]
+class NotificationPreference extends Model
+{
+    /**
+     * @return BelongsTo<User, $this>
+     */
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    /**
+     * @return array<string, string>
+     */
+    protected function casts(): array
+    {
+        return [
+            'comment_on_presentation' => 'boolean',
+            'form_reply' => 'boolean',
+            'new_follower' => 'boolean',
+            'news_announcements' => 'boolean',
+            'weekly_product_updates' => 'boolean',
+            'weekly_blog_digest' => 'boolean',
+        ];
+    }
+}