feat(workshop): allow admin/owner to delete service orders

- Soft-delete service orders via is_deleted flag.

- Added DELETE /pos/api/service-orders/<id> restricted to owner/admin.

- Updated list, detail, summary, status and assignment queries to exclude deleted orders.

- Added 'Eliminar orden' button in the detail modal for administrators.

pos/migrations/v4.12_service_order_soft_delete.sql

@@ -0,0 +1,11 @@
+-- v4.12_service_order_soft_delete.sql
+-- Soft-delete support for service orders.
+
+ALTER TABLE service_orders
+    ADD COLUMN IF NOT EXISTS is_deleted BOOLEAN NOT NULL DEFAULT FALSE;
+
+CREATE INDEX IF NOT EXISTS idx_service_orders_is_deleted
+    ON service_orders (is_deleted);
+
+-- Exclude deleted orders from common queries by default via partial index helpers
+-- (application filters explicitly).