feat(configurator): C3 — link direct-order line to a prior quote

Adds quote_id (Many2one fp.quote.configurator) on the wizard line
with a domain scoped to the wizard's customer + quote states (sent /
accepted / won). Onchange auto-fills part, coating, and unit price
(final = estimator_override_price or calculated_price, per-part).

Mirrors x_fc_quote_id on sale.order.line for the audit trail. Surfaced
as a togglable column on the SO line tree and under "Qty & Price" on
the wizard line drill-in form.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_configurator/models/sale_order_line.py

@@ -41,3 +41,8 @@ class SaleOrderLine(models.Model):
         help='Flag for prototype / non-catalog parts that should not be '
              'reused after this order.',
     )
+    x_fc_quote_id = fields.Many2one(
+        'fp.quote.configurator',
+        string='Linked Quote',
+        help='Quote that seeded this line. Links back for audit trail.',
+    )