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/static/js/sidebar.js

@@ -40,6 +40,7 @@ window.renderSidebar = function(modulesOverride) {
         ].filter(Boolean)},
         { label: _t('nav_management'), items: [
             { name: _t('customers'), href: '/pos/customers', icon: '<path d="M17 21v-2a4 4 0 0 0-4-4H5a4 4 0 0 0-4 4v2"/><circle cx="9" cy="7" r="4"/><path d="M23 21v-2a4 4 0 0 0-3-3.87M16 3.13a4 4 0 0 1 0 7.75"/>' },
+            { name: 'Taller', href: '/pos/workshop', icon: '<path d="M14.7 6.3a1 1 0 0 0 0 1.4l1.6 1.6a1 1 0 0 0 1.4 0l3.77-3.77a6 6 0 0 1-7.94 7.94l-6.91 6.91a2.12 2.12 0 0 1-3-3l6.91-6.91a6 6 0 0 1 7.94-7.94l-3.76 3.76z"/>' },
             { name: 'Cotizaciones', href: '/pos/quotations', icon: '<path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"/><polyline points="14 2 14 8 20 8"/><line x1="9" y1="15" x2="15" y2="15"/><line x1="12" y1="12" x2="12" y2="18"/>' },
             moduleEnabled('marketplace') ? { name: 'Marketplace', href: '/pos/marketplace', icon: '<circle cx="9" cy="21" r="1"/><circle cx="20" cy="21" r="1"/><path d="M1 1h4l2.68 13.39a2 2 0 0 0 2 1.61h9.72a2 2 0 0 0 2-1.61L23 6H6"/>' } : null,
             moduleEnabled('meli') ? { name: 'MercadoLibre', href: '/pos/marketplace-external', icon: '<rect x="2" y="3" width="20" height="14" rx="2"/><path d="M8 21h8M12 17v4"/>' } : null,