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/onboard-customer.dto.ts

@@ -0,0 +1,56 @@
+import {
+  ArrayMaxSize,
+  IsArray,
+  IsEnum,
+  IsIn,
+  IsNumber,
+  IsOptional,
+  IsString,
+  MinLength,
+  ValidateNested,
+} from "class-validator";
+import { Type } from "class-transformer";
+import { Currency } from "@jorgecuadros/database";
+import { CreateCustomerDto } from "./create-customer.dto";
+import { ServiceDto } from "../properties/property.dto";
+
+/** The property, minus the customer it is being created for. */
+export class OnboardPropertyDto {
+  @IsOptional() @IsString() addressLine1?: string;
+  @IsOptional() @IsString() addressLine2?: string;
+  @IsOptional() @IsString() phone1?: string;
+}
+
+/**
+ * The opening balance the office takes when an account is opened, captured as
+ * the customer's first payment. Cash issues an EFE receipt; a check posts a
+ * CHECK DEPOSIT against that check number.
+ */
+export class OpeningPaymentDto {
+  @IsIn(["CASH", "CHECK"]) method!: "CASH" | "CHECK";
+  @IsNumber() amount!: number;
+  @IsEnum(Currency) currency!: Currency;
+  @IsString() @MinLength(1) receivedAt!: string;
+  @IsOptional() @IsString() checkNumber?: string;
+  /** Cash only: dollars credited to a pesos ledger. */
+  @IsOptional() @IsNumber() exchangeRate?: number;
+  @IsOptional() @IsString() concept?: string;
+}
+
+/** One screen: cliente + propiedad + servicios + saldo inicial. */
+export class OnboardCustomerDto {
+  @ValidateNested() @Type(() => CreateCustomerDto) customer!: CreateCustomerDto;
+
+  @IsOptional() @ValidateNested() @Type(() => OnboardPropertyDto)
+  property?: OnboardPropertyDto;
+
+  @IsOptional()
+  @IsArray()
+  @ArrayMaxSize(12)
+  @ValidateNested({ each: true })
+  @Type(() => ServiceDto)
+  services?: ServiceDto[];
+
+  @IsOptional() @ValidateNested() @Type(() => OpeningPaymentDto)
+  openingPayment?: OpeningPaymentDto;
+}