feat(clientes): alta de cliente in one screen, opening balance as a payment

The 2026-10-08 ask: open an account without four screens — cliente,
propiedad, servicios and the saldo inicial, taken as the first payment.

POST /customers/onboard writes it all in one Prisma transaction; a bad
service or a taken folder number leaves nothing behind (rolled back on dev).
A cash opening balance goes through the EFE receipt book inside that same
transaction, so it gets its folio and its C<folio> credit; a check posts a
CHECK DEPOSIT against the number given. /clientes/alta pre-fills the next
free folder number and links the receipt for printing. The old
customer-only form stays as "Solo cliente".

Built without the screen sketch from the meeting (it never arrived); the
fields are the legacy ones.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/src/customers/customers.controller.ts

@@ -19,6 +19,7 @@ import { CustomersService } from "./customers.service";
 import { NumidService } from "./numid.service";
 import { CreateCustomerDto } from "./create-customer.dto";
 import { UpdateCustomerDto } from "./update-customer.dto";
+import { OnboardCustomerDto } from "./onboard-customer.dto";
 
 @UseGuards(AuthenticatedGuard, AbilityGuard)
 @Controller("customers")
@@ -83,6 +84,26 @@ export class CustomersController {
     return c;
   }
 
+  /**
+   * Alta en una pantalla. Gated on customer:create; the property, service and
+   * ledger abilities it also exercises sit at the same STAFF tier.
+   */
+  @Post("onboard")
+  @RequireAbility("customer:create")
+  async onboard(@Body() dto: OnboardCustomerDto, @Req() req: Request) {
+    const r = await this.customers.onboard(dto, this.actingId(req));
+    void this.audit.log(this.actingId(req), "customer.onboard", {
+      customerId: r.customer.id,
+      name: r.customer.name,
+      folderNumber: r.customer.folderNumber,
+      propertyId: r.property?.id,
+      services: dto.services?.length ?? 0,
+      folio: r.receipt?.folio,
+      openingTransactionId: r.receipt?.transactionId ?? r.payment?.id,
+    });
+    return r;
+  }
+
   @Patch(":id")
   @RequireAbility("customer:update")
   async update(