feat: add whatsapp_number field to suppliers, customers, users

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

app/Models/Customer.php

@@ -9,7 +9,7 @@ class Customer extends Model
 {
     use HasFactory;
 
-    protected $fillable = ['name', 'contact_person', 'email', 'phone', 'address', 'tax_number', 'credit_limit', 'outstanding_balance', 'is_active'];
+    protected $fillable = ['name', 'contact_person', 'email', 'phone', 'whatsapp_number', 'address', 'tax_number', 'credit_limit', 'outstanding_balance', 'is_active'];
 
     protected $casts = [
         'credit_limit' => 'decimal:2',
@@ -17,6 +17,11 @@ class Customer extends Model
         'is_active' => 'boolean',
     ];
 
+    public function routeNotificationFor(string $channel, mixed $notification = null): ?string
+    {
+        return $this->whatsapp_number;
+    }
+
     public function salesOrders()
     {
         return $this->hasMany(SalesOrder::class);