feat(billing): default the 7-day demo to 3 users

Applying or creating a trial plan sets the owner seat cap to 3, and existing demos without a cap get the same default.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/prisma/migrations/20261102200000_trial_default_max_users/migration.sql

@@ -0,0 +1,4 @@
+-- دموی ۷ روزه که هنوز سقف کاربر ندارد، پیش‌فرض ۳ کاربر می‌گیرد
+UPDATE "BillingAccount"
+SET "maxUsers" = 3
+WHERE "planCode" = 'trial' AND "maxUsers" IS NULL;

apps/api/src/billing/billing.service.ts

@@ -159,6 +159,7 @@ export class BillingService {
         startsAt: now,
         expiresAt,
         maxOrganizations: Math.max(1, opts?.maxOrganizations ?? 1),
+        maxUsers: 3,
       },
     });
   }
@@ -301,6 +302,7 @@ export class BillingService {
             expiresAt,
             maxOrganizations,
             expiryNotifiedAt,
+            ...(planCode === 'trial' ? { maxUsers: 3 } : {}),
             ...(dto.notes !== undefined ? { notes: dto.notes } : {}),
           },
         })
@@ -314,6 +316,7 @@ export class BillingService {
             maxOrganizations,
             notes: dto.notes ?? null,
             expiryNotifiedAt,
+            ...(planCode === 'trial' ? { maxUsers: 3 } : {}),
           },
         });
     if (status === 'expired' && !expiryNotifiedAt) {