Kod tekshiruvi va sifat nazorati

## Nima qilindi
Buyurtma bekor qilish imkoniyati qo'shildi.

## Nima uchun
Mijozlar noto'g'ri buyurtma bergan holatda qo'llab-quvvatlashga
qo'ng'iroq qilishga majbur edi (oyiga ~40 murojaat).

## Qanday tekshirish
1. Yangi buyurtma yarating
2. "Bekor qilish" tugmasini bosing
3. Buyurtma holati "bekor" ga o'zgarganini tekshiring
4. Ombor qaytarilganini tekshiring

## E'tibor bering
- `BuyurtmaHolati` enum ga o'tish qoidalari qo'shildi
- Bekor qilish faqat "yangi" va "tolangan" holatlarida mumkin
- Ombor qaytarish tranzaksiya ichida

Fixes #142

composer require --dev phpstan/phpstan
vendor/bin/phpstan analyse manba/ --level=8

# phpstan.neon
parameters:
    level: 8
    paths:
        - manba
        - testlar
    excludePaths:
        - manba/Migratsiyalar/*
    checkMissingIterableValueType: true

// Siklomatik murakkablik = 8
public function narxHisoblang(Buyurtma $b, Mijoz $m, ?Kupon $k): float
{
    $narx = $b->jami();

    if ($m->daraja() === 'oltin') {              // +1
        $narx *= 0.9;
    } elseif ($m->daraja() === 'kumush') {       // +1
        $narx *= 0.95;
    }

    if ($k !== null) {                            // +1
        if ($k->amalQiladimi()) {                 // +1
            if ($k->turi() === 'foiz') {          // +1
                $narx *= (1 - $k->qiymat() / 100);
            } else {                              // +1
                $narx -= $k->qiymat();
            }
        }
    }

    if ($narx < 0) {                              // +1
        $narx = 0;
    }

    return $narx;
}

Haydovchi (Driver):  klaviatura oldida, kod yozadi
Navigator:           o'ylaydi, yo'nalish beradi, xatolarni sezadi

Har 15-30 daqiqada rollar almashadi

# .github/workflows/sifat.yml
name: Kod sifati

on: [pull_request]

jobs:
  tekshiruv:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: shivammathur/setup-php@v2
        with:
          php-version: '8.3'
          coverage: xdebug

      - run: composer install --prefer-dist --no-progress

      - name: Kod uslubi
        run: vendor/bin/php-cs-fixer fix --dry-run --diff

      - name: Statik tahlil
        run: vendor/bin/phpstan analyse --error-format=github

      - name: Testlar
        run: vendor/bin/phpunit --coverage-clover=coverage.xml

      - name: Xavfsizlik
        run: composer audit

      - name: Qoplama tekshiruvi
        run: |
          FOIZ=$(php -r '
            $x = simplexml_load_file("coverage.xml");
            $m = $x->project->metrics;
            echo round((int)$m["coveredstatements"] / (int)$m["statements"] * 100);
          ')
          echo "Qoplama: ${FOIZ}%"
          if [ "$FOIZ" -lt 70 ]; then
            echo "Qoplama 70% dan past"
            exit 1
          fi