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/v4.4_workshop.sql

@@ -0,0 +1,66 @@
+-- v4.4 Workshop Lite
+-- Extends service orders with inventory reservation, sale linking and a labor catalog.
+
+-- ═════════════════════════════════════════════════════════════════════════════
+-- 1. SERVICE_ORDERS: link to the sale generated from the order
+-- ═════════════════════════════════════════════════════════════════════════════
+ALTER TABLE service_orders
+    ADD COLUMN IF NOT EXISTS sale_id INTEGER REFERENCES sales(id);
+
+COMMENT ON COLUMN service_orders.sale_id IS 'Sale/invoice generated from this service order';
+
+CREATE INDEX IF NOT EXISTS idx_service_orders_sale_id ON service_orders(sale_id);
+
+-- ═════════════════════════════════════════════════════════════════════════════
+-- 2. SERVICE_CATALOG: reusable labor/work concepts for mechanics
+-- ═════════════════════════════════════════════════════════════════════════════
+CREATE TABLE IF NOT EXISTS service_catalog (
+    id SERIAL PRIMARY KEY,
+    tenant_id INTEGER NOT NULL,
+    name VARCHAR(200) NOT NULL,
+    description TEXT,
+    suggested_hours NUMERIC(6,2) DEFAULT 0,
+    suggested_rate NUMERIC(12,2) DEFAULT 0,
+    is_active BOOLEAN DEFAULT true,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_service_catalog_tenant ON service_catalog(tenant_id);
+CREATE INDEX IF NOT EXISTS idx_service_catalog_active ON service_catalog(is_active);
+
+COMMENT ON TABLE service_catalog IS 'Reusable labor concepts for workshop service orders';
+
+-- Trigger to auto-update updated_at on service_catalog
+CREATE OR REPLACE FUNCTION update_service_catalog_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = NOW();
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS trg_service_catalog_updated_at ON service_catalog;
+CREATE TRIGGER trg_service_catalog_updated_at
+    BEFORE UPDATE ON service_catalog
+    FOR EACH ROW
+    EXECUTE FUNCTION update_service_catalog_updated_at();
+
+-- ═════════════════════════════════════════════════════════════════════════════
+-- 3. SERVICE_ORDER_ITEMS: track reserved quantity separately
+-- ═════════════════════════════════════════════════════════════════════════════
+ALTER TABLE service_order_items
+    ADD COLUMN IF NOT EXISTS reserved_quantity NUMERIC(10,2) DEFAULT 0;
+
+COMMENT ON COLUMN service_order_items.reserved_quantity IS 'Quantity currently reserved from inventory';
+
+-- ═════════════════════════════════════════════════════════════════════════════
+-- 4. INVENTORY_OPERATIONS: new operation types for service orders
+-- ═════════════════════════════════════════════════════════════════════════════
+-- operation_type is VARCHAR(20) without a constraint, so no ALTER is needed.
+-- New types used by the workshop module:
+--   SO_RESERVE  : negative quantity, reserves stock when item is added to SO
+--   SO_RELEASE  : positive quantity, releases a previous reservation
+--   SO_CONSUME  : negative quantity, final deduction when SO is converted to sale
+COMMENT ON COLUMN inventory_operations.operation_type IS
+    'SALE, PURCHASE, RETURN, ADJUST, TRANSFER, INITIAL, QUOTE_RESERVE, QUOTE_RELEASE, SO_RESERVE, SO_RELEASE, SO_CONSUME';