feat(jobs): persist deadlines + planned start + notes on fp.job

Tier 2 of the SO->fp.job persistence audit. Four operational metadata
fields mirrored from sale.order:

- x_fc_internal_deadline (Date) - shop's internal target finish date,
  ahead of the customer-facing deadline. Kept separate from
  date_deadline (which scheduling code may adjust).
- x_fc_planned_start_date (Date) - customer-quoted planned start date.
  Kept separate from date_planned_start (Datetime, capacity-adjusted).
- x_fc_internal_note (Text) - shop-internal notes from the order.
- x_fc_external_note (Text) - customer-facing notes, printed on
  traveller / BoL / cert.

All four populate at SO confirm via _fp_auto_create_job, and surface
on sale.order.line as stored related fields for per-line visibility.
fp.job form view gets a Notes group alongside the Customer References
group from Tier 1.

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

fusion_plating/fusion_plating_jobs/models/sale_order.py

@@ -332,6 +332,22 @@ class SaleOrder(models.Model):
             if 'x_fc_rush_order' in self._fields:
                 vals['x_fc_rush_order'] = bool(self.x_fc_rush_order)
 
+            # Scheduling targets — mirror the SO's customer-facing dates.
+            if 'x_fc_internal_deadline' in self._fields \
+                    and self.x_fc_internal_deadline:
+                vals['x_fc_internal_deadline'] = self.x_fc_internal_deadline
+            if 'x_fc_planned_start_date' in self._fields \
+                    and self.x_fc_planned_start_date:
+                vals['x_fc_planned_start_date'] = self.x_fc_planned_start_date
+
+            # Operational notes — mirror so the shop has them on the WO.
+            if 'x_fc_internal_note' in self._fields \
+                    and self.x_fc_internal_note:
+                vals['x_fc_internal_note'] = self.x_fc_internal_note
+            if 'x_fc_external_note' in self._fields \
+                    and self.x_fc_external_note:
+                vals['x_fc_external_note'] = self.x_fc_external_note
+
             # Customer spec / facility / manager — copy from SO if present
             if 'x_fc_customer_spec_id' in self._fields and self.x_fc_customer_spec_id:
                 vals['customer_spec_id'] = self.x_fc_customer_spec_id.id