feat(fin,ops): Facturación y Cobranza (Diag. 4), bitácora de embarque (Diag. 3) y subida a MinIO

- schema fin: fin.invoices + fin.invoice_items + fin.payments; totales con IVA,
  estados borrador→emitida→enviada→pagada, cobranza (pagos) y saldo automático
- generar-factura-desde-embarque (toma conceptos de venta de la cotización)
- ops.shipment_events: bitácora/hitos del embarque con secuencia por defecto
  según operación (importación/exportación) — cubre Diagrama 3
- subida de documentos a MinIO: POST /crm/uploads (multipart) + URL firmada
- migración c4d5e6f7a8b9, routers/permisos (fin), seed del flujo hasta factura
- 58 tests pytest en verde

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/tests/test_shipment_events.py

@@ -0,0 +1,34 @@
+import pytest
+from fastapi import HTTPException
+
+from api.v1.modules.ops.shipments import service
+from api.v1.modules.ops.shipments.dto import ShipmentCreate
+
+T, C = 1, 1
+
+
+def test_seed_import_milestones(db):
+    s = service.create_shipment(db, ShipmentCreate(reference="IMP-1", operation_type="importacion"), T, C)
+    events = service.seed_default_milestones(db, s.id, T, C)
+    titles = [e.event_type for e in events]
+    assert "aviso_llegada" in titles
+    assert "despacho_importacion" in titles
+    assert "entrega" in titles
+    # idempotente: no duplica
+    again = service.seed_default_milestones(db, s.id, T, C)
+    assert len(again) == len(events)
+
+
+def test_seed_export_milestones_and_complete(db):
+    s = service.create_shipment(db, ShipmentCreate(reference="EXP-1", operation_type="exportacion"), T, C)
+    events = service.seed_default_milestones(db, s.id, T, C)
+    assert any(e.event_type == "embarque" for e in events)
+    done = service.complete_shipment_event(db, events[0].id, T, C)
+    assert done.status == "completado" and done.actual_date is not None
+
+
+def test_seed_requires_operation_type(db):
+    s = service.create_shipment(db, ShipmentCreate(reference="X-1"), T, C)  # sin operation_type
+    with pytest.raises(HTTPException) as exc:
+        service.seed_default_milestones(db, s.id, T, C)
+    assert exc.value.status_code == 422