feat(partners): add utility functions for partner business activity allocation limits and remaining licenses

- Implemented `getPartnerBusinessActivityAllocationLimits` to retrieve allocation limits for a partner's business activity.
- Added `ensurePartnerBusinessActivityHasRemainingAllocation` to validate remaining allocation credits.
- Created `getPartnerRemainingLicenses` to count remaining licenses for a partner.
- Developed `getPartnerFirstRemainingLicense` to fetch the first unused license for a partner.
- Introduced `ensurePartnerHasRemainingLicense` to ensure a partner has at least one unused license.

prisma/schema/admin/partners.prisma

@@ -5,7 +5,7 @@ model PartnerAccount {
   created_at DateTime @default(now()) @db.Timestamp(0)
   updated_at DateTime @default(now()) @updatedAt @db.Timestamp(0)
 
-  partner_id String
+  partner_id String  @unique
   partner    Partner @relation(fields: [partner_id], references: [id])
 
   account_id String  @unique