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/models/fp_job.py

@@ -289,6 +289,37 @@ class FpJob(models.Model):
              'job form to know it\'s rush.',
     )
 
+    # ---- Scheduling targets mirrored from sale.order -----------------
+    # These are kept separate from the operational date_planned_start /
+    # date_deadline fields (which may be tweaked by scheduling logic) —
+    # this preserves the ORIGINAL customer-facing dates entered on the SO.
+    x_fc_internal_deadline = fields.Date(
+        string='Internal Deadline',
+        tracking=True,
+        help='Shop\'s internal target finish date, copied from sale.order. '
+             'Buffer ahead of the customer-facing deadline.',
+    )
+    x_fc_planned_start_date = fields.Date(
+        string='Planned Start (SO)',
+        tracking=True,
+        help='Customer-quoted planned start date copied from sale.order. '
+             'Different from date_planned_start (which scheduling logic '
+             'may adjust based on shop capacity).',
+    )
+
+    # ---- Operational notes mirrored from sale.order ------------------
+    x_fc_internal_note = fields.Text(
+        string='Internal Note',
+        tracking=True,
+        help='Shop-internal notes from the order. Not shown to customer.',
+    )
+    x_fc_external_note = fields.Text(
+        string='External Note',
+        tracking=True,
+        help='Customer-facing notes copied from the sale order. Printed '
+             'on traveller / BoL / cert.',
+    )
+
     qty_received = fields.Integer(
         string='Qty Received',
         help='Paper traveller "Qty Rec." column.',