Feature: add the possibility to redeem vouchers multiple times with limit

For example:

A school class (30 students) can redeem a code for their class.
But you want to count on how many times the voucher has been redeemd.

After 30 redeems, the voucher is no longer valid.

Code example:

1. Migration

```
Schema::create('vouchers', function (Blueprint $table) {
$table->id();
$table->string('code')->unique();
$table->integer('max_redeems')->default(30); // new
$table->integer('current_redeems')->default(0); // new
$table->timestamps();
});
```

2. Model

```
class Voucher extends Model
{
protected $fillable = ['code', 'max_redeems', 'current_redeems'];

public function isValid()
{
return $this->current_redeems < $this->max_redeems;
}

public function redeem()
{
if ($this->isValid()) {
$this->current_redeems++;
$this->save();
return true;
}
return false;
}
}
```

Start by locating the voucher migration and Voucher model described in the issue, then trace the existing redemption entry point. Check how voucher validity and persistence currently work, and verify the final behavior with the project's existing tests or redemption flow: a voucher should succeed until its configured limit and fail afterward.

Written by the indexing model from the issue text.