feat(pos/workshop): add lightweight workshop/taller module

- Add DB migration v4.4_workshop.sql (sale_id, service_catalog,
  reserved_quantity, SO_RESERVE/SO_RELEASE operation types).
- Extend service_order_engine with inventory reservation, release,
  convert-to-sale, mechanic assignment, and service catalog CRUD.
- Extend service_order_bp with /reserve, /convert-to-sale,
  /assign-mechanic, and /service-catalog endpoints.
- Create workshop Kanban UI: workshop.html, workshop.js, workshop.css.
- Add /pos/workshop route and sidebar navigation (sidebar.js + inline
  templates).
- Add 11 unit tests with mocked cursors.
- Update FASES_IMPLEMENTADAS.md with FASE 9 documentation.

Tests: 92 passing (61 console + 20 Facturapi + 11 workshop).

pos/migrations/runner.py

@@ -50,6 +50,7 @@ MIGRATIONS = {
     "v4.1": "v4.1_global_invoice.sql",
     "v4.2": "v4.2_meli_sync_queue.sql",
     "v4.3": "v4.3_facturapi.sql",
+    "v4.4": "v4.4_workshop.sql",
 }