feat(crm): dominio backend (cuentas, contactos, prospectos, embudos, oportunidades, actividades)

- Nuevo schema `crm` con 7 tablas multi-tenant (TenantScopedMixin + soft delete)
- Módulos FastAPI por dominio: models/dto/service/routes (patrón example)
- Métricas del dashboard (KPIs + embudo por etapa)
- Conversión de prospecto → cuenta/contacto/oportunidad (idempotente)
- Movimiento de oportunidad entre etapas (Kanban) con estado/probabilidad derivados
- 25 permisos registrados en PermissionRegistry
- Migración Alembic con upgrade/downgrade completos
- 24 tests de servicios (pytest) en verde

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

backend/api/v1/modules/crm/accounts/service.py

@@ -0,0 +1,73 @@
+from datetime import datetime, timezone
+
+from fastapi import HTTPException, status
+from sqlalchemy.orm import Session
+
+from .dto import AccountCreate, AccountUpdate
+from .models import Account
+
+
+def get_accounts(
+    db: Session,
+    tenant_id: int,
+    company_id: int,
+    search: str | None = None,
+    account_status: str | None = None,
+) -> list[Account]:
+    query = db.query(Account).filter(
+        Account.tenant_id == tenant_id,
+        Account.company_id == company_id,
+        Account.deleted_at.is_(None),
+    )
+    if search:
+        pattern = f"%{search}%"
+        query = query.filter(
+            Account.name.ilike(pattern)
+            | Account.trade_name.ilike(pattern)
+            | Account.rfc.ilike(pattern)
+        )
+    if account_status:
+        query = query.filter(Account.status == account_status)
+    return query.order_by(Account.name.asc()).all()
+
+
+def get_account(db: Session, account_id: int, tenant_id: int, company_id: int) -> Account:
+    account = (
+        db.query(Account)
+        .filter(
+            Account.id == account_id,
+            Account.tenant_id == tenant_id,
+            Account.company_id == company_id,
+            Account.deleted_at.is_(None),
+        )
+        .first()
+    )
+    if not account:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Cuenta no encontrada")
+    return account
+
+
+def create_account(db: Session, payload: AccountCreate, tenant_id: int, company_id: int) -> Account:
+    account = Account(**payload.model_dump(), tenant_id=tenant_id, company_id=company_id)
+    db.add(account)
+    db.commit()
+    db.refresh(account)
+    return account
+
+
+def update_account(
+    db: Session, account_id: int, payload: AccountUpdate, tenant_id: int, company_id: int
+) -> Account:
+    account = get_account(db, account_id, tenant_id, company_id)
+    for field, value in payload.model_dump(exclude_unset=True).items():
+        setattr(account, field, value)
+    db.commit()
+    db.refresh(account)
+    return account
+
+
+def delete_account(db: Session, account_id: int, tenant_id: int, company_id: int) -> None:
+    account = get_account(db, account_id, tenant_id, company_id)
+    # Soft delete: conserva el histórico comercial de la cuenta
+    account.deleted_at = datetime.now(timezone.utc)
+    db.commit()