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_configurator/models/sale_order_line.py

@@ -659,3 +659,28 @@ class SaleOrderLine(models.Model):
         readonly=True,
         store=True,
     )
+
+    x_fc_internal_deadline = fields.Date(
+        related='order_id.x_fc_internal_deadline',
+        string='Internal Deadline',
+        readonly=True,
+        store=True,
+    )
+    x_fc_planned_start_date = fields.Date(
+        related='order_id.x_fc_planned_start_date',
+        string='Planned Start',
+        readonly=True,
+        store=True,
+    )
+    x_fc_internal_note = fields.Text(
+        related='order_id.x_fc_internal_note',
+        string='Internal Note',
+        readonly=True,
+        store=True,
+    )
+    x_fc_external_note = fields.Text(
+        related='order_id.x_fc_external_note',
+        string='External Note',
+        readonly=True,
+        store=True,
+    )