feat(fusion_claims): allow order-less tasks + service-repair SO flag

Relaxes _check_order_link to a no-op (service bookings auto-create their SO;
in-shop/walk-in tasks may have none) and adds x_fc_is_service_repair on
sale.order. The 'Service Repair' crm.tag from the plan is intentionally
omitted: fusion_claims does not depend on crm and sale.order has no tag_ids;
the boolean flag is the repair-SO identity.

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

fusion_claims/models/sale_order.py

@@ -338,6 +338,11 @@ class SaleOrder(models.Model):
         help='Type of sale for billing purposes. This field determines the workflow and billing rules.',
     )
     
+    x_fc_is_service_repair = fields.Boolean(
+        string='Service Repair', copy=False,
+        help='Auto-created from the technician service booking wizard.',
+    )
+
     x_fc_sale_type_locked = fields.Boolean(
         string='Sale Type Locked',
         compute='_compute_sale_type_locked',