fix architecture and write new tests

apps/api/src/services/pricingRuleService.ts

@@ -13,7 +13,7 @@ export async function applyPricingRules(
   totalDays: number
 ): Promise<{ applied: any[]; total: number }> {
   const rules = await prisma.pricingRule.findMany({ where: { companyId, isActive: true } })
-  const customer = await prisma.customer.findUniqueOrThrow({ where: { id: customerId } })
+  const customer = await prisma.customer.findFirstOrThrow({ where: { id: customerId, companyId } })
   const allDrivers: DriverInfo[] = [customer, ...additionalDrivers]
   const applied: any[] = []
   const baseAmount = dailyRate * totalDays