feat(customers): create/edit/archive CRUD with soft-delete (plan phase 2)

First master-data CRUD module on the phase-1 RBAC foundation.

API:
- Customer gains archivedAt (soft-delete marker, distinct from the legacy
  `status` business flag); pushed to dev (nullable, non-destructive).
- CustomersService: create/update/archive/restore. list() and the browser
  default to archivedAt=null; ?includeArchived=true opts in. App-created
  rows set nameMissing=false and leave legacy provenance null.
- CustomersController write routes guarded per the matrix: create/update
  need STAFF+ (customer:create/update), archive/restore need ADMIN
  (customer:delete). Every mutation audit-logged.
- create/update DTOs (class-validator); date strings coerced to Date.

Web:
- Shared CustomerForm (create + edit) with identity/address/account
  sections; new routes /clientes/nuevo and /clientes/[id]/editar, each
  self-gated on the ability.
- List page: ability-gated "Nuevo cliente" button. Detail page: gated
  Editar / Archivar (Restaurar) action bar; archived badge.
- api.ts create/update/archive/restore; CustomerInput type; archived flag
  on list items.

Verified against dev: create (dates coerced, archivedAt null), edit 200,
VIEWER create 403, STAFF create 201 but archive 403, ADMIN archive drops
the row from the default list and includeArchived surfaces it, restore
returns it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/database/prisma/schema.prisma

@@ -83,6 +83,10 @@ model Customer {
   minimumBalance            Decimal?  @db.Decimal(12, 2)
   feeAmount                 Decimal?  @db.Decimal(12, 2)
   preferredCurrency         Currency  @default(USD)
+  // Soft-delete marker. Distinct from `status` (a legacy business flag): a
+  // non-null archivedAt hides the row from default lists while preserving it
+  // and its legacy provenance. Never hard-delete migrated data.
+  archivedAt                DateTime?
   createdAt                 DateTime  @default(now())
   updatedAt                 DateTime  @updatedAt