feat(jobs): persist Customer Job # + PO # + Rush Order on fp.job

Tier 1 of the SO->fp.job persistence audit. Three customer-reference
fields entered on sale.order's Plating tab were not flowing through
to fp.job (or SO lines), so the shop floor and printed paperwork
(traveller, BoL, cert) had to round-trip via sale_order_id every time.

Changes:
- fp.job: new x_fc_customer_job_number (Char, tracking), x_fc_po_number
  (Char, tracking), x_fc_rush_order (Boolean, tracking). All three
  populated by _fp_auto_create_job at SO confirm time.
- sale.order.line: x_fc_customer_job_number / x_fc_po_number added as
  stored related fields off order_id so per-line list views show the
  customer's references without navigating to the order header
  (x_fc_rush_order was already on lines).
- fp.job form view: small Customer References group under the title
  surfaces the three fields where the user expects them.

Verified end-to-end: SO -> SO line related fields -> fp.job direct
fields all carry the same value.

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

fusion_plating/fusion_plating/views/fp_job_views.xml

@@ -37,6 +37,11 @@
                     <div class="oe_title">
                         <h1><field name="display_name" readonly="1"/></h1>
                     </div>
+                    <group name="x_fc_customer_refs">
+                        <field name="x_fc_customer_job_number"/>
+                        <field name="x_fc_po_number"/>
+                        <field name="x_fc_rush_order"/>
+                    </group>
                     <group>
                         <group>
                             <field name="partner_id"/>