Show linked domains on cards and fix Email leftovers.

Display hosted_sites on account cards, scope Afia and Settings to hosting,
add hosting_settings for notifications, and remove mailbox UI from the
hosting layout and account pages.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Models/HostingSetting.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+/** Per-account hosting preferences (notifications, product updates). */
+class HostingSetting extends Model
+{
+    protected $fillable = ['user_id', 'notify_email', 'product_updates'];
+
+    protected $casts = ['product_updates' => 'boolean'];
+}