fix: remove invalid default on CashboxExportSubscription.recipients

MySQL/MariaDB reject a DEFAULT value on TEXT-backed columns (TypeORM's
simple-array maps to TEXT), so table creation failed with
"BLOB, TEXT, GEOMETRY or JSON column 'recipients' can't have a default
value". The service always assigns recipients before saving, so no
DB-level default was ever needed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

myteamwallet_backend/src/cashbox-export/entities/cashbox-export-subscription.entity.ts

@@ -12,7 +12,7 @@ export class CashboxExportSubscription extends EntityHelper {
   @JoinColumn()
   team: Team;
 
-  @Column({ type: 'simple-array', default: '' })
+  @Column({ type: 'simple-array' })
   recipients: string[];
 
   @Column()