feat(crm): Expediente — referencia única de trazabilidad del trámite (Fase D)

- Tabla crm.cases (expediente) con folio EXP2026-08-001 (next_folio entidad EXP,
  sin dirección). Nace al crear la Oportunidad y se hereda vía case_id a
  solicitud → cotización → operación → factura. advance_stage solo avanza.
- case_id (FK a crm.cases) en crm.opportunities/service_requests/quotes,
  ops.shipments y fin.invoices; propagación en sus create_*. Migración
  d4e5f6a7b8c9 reversible.
- Endpoints GET /v1/crm/cases, /cases/{id}, /cases/by-ref/{ref} con timeline
  (historia completa para UI y otros sistemas).
- Frontend: casesAPI, ruta /dashboard/crm/expedientes (lista + timeline vertical),
  chip "📁 Expediente" en solicitud/cotización, "Expedientes" en el sidebar.
- Consecutivo de folios sin tope (soporta >10,000,000/mes).
- 4 pruebas de expediente (minteo, propagación, timeline, no-retroceso). Suite en verde (113).

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

backend/api/v1/modules/fin/invoices/dto.py

@@ -100,6 +100,7 @@ class InvoiceResponse(InvoiceBase):
     model_config = ConfigDict(from_attributes=True)
 
     id: int
+    case_id: int | None = None
     status: str
     subtotal: Decimal
     tax_amount: Decimal

backend/api/v1/modules/fin/invoices/models.py

@@ -15,6 +15,7 @@ class Invoice(Base, TenantScopedMixin, TimestampMixin):
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
     reference: Mapped[str | None] = mapped_column(String(40), nullable=True, index=True)  # folio
+    case_id: Mapped[int | None] = mapped_column(Integer, ForeignKey("crm.cases.id"), nullable=True, index=True)  # expediente
     shipment_id: Mapped[int | None] = mapped_column(
         Integer, ForeignKey("ops.shipments.id"), nullable=True, index=True
     )

backend/api/v1/modules/fin/invoices/service.py

@@ -6,6 +6,7 @@ from sqlalchemy import func
 from sqlalchemy.orm import Session
 
 from api.v1.modules.crm.accounts.models import Account
+from api.v1.modules.crm.cases import service as cases_service
 from api.v1.modules.crm.common.folios import next_folio
 from api.v1.modules.crm.quotes.models import Quote, QuoteItem
 from api.v1.modules.ops.shipments.models import Shipment
@@ -99,6 +100,12 @@ def create_invoice(db, payload: InvoiceCreate, tenant_id, company_id, user_id=No
     # Folio F... auto-generado (mensual) si no viene uno explícito
     if not obj.reference:
         obj.reference = next_folio(db, tenant_id, company_id, "F", None, with_direction=False)
+    # Expediente heredado del embarque (si la factura se genera de uno)
+    if obj.shipment_id and not obj.case_id:
+        sh = db.query(Shipment).filter(Shipment.id == obj.shipment_id).first()
+        if sh:
+            obj.case_id = sh.case_id
+    cases_service.advance_stage(db, obj.case_id, "facturacion")
     db.add(obj)
     db.flush()
     _recompute(db, obj)
@@ -285,6 +292,7 @@ def generate_from_shipment(db, shipment_id, tenant_id, company_id, user_id=None)
 
     invoice = Invoice(
         reference=shipment.reference,
+        case_id=shipment.case_id,
         shipment_id=shipment.id,
         quote_id=shipment.quote_id,
         account_id=shipment.account_id,
@@ -298,6 +306,7 @@ def generate_from_shipment(db, shipment_id, tenant_id, company_id, user_id=None)
     )
     db.add(invoice)
     db.flush()
+    cases_service.advance_stage(db, shipment.case_id, "facturacion")
 
     if quote:
         q_items = db.query(QuoteItem).filter(QuoteItem.quote_id == quote.id, QuoteItem.deleted_at.is_(None)).all()