feat(configurator): stub fp.direct.order.line model for multi-line direct order wizard

Task A1 of the direct-order-wizard rewrite. Adds the transient line
model that will hold per-part detail (part, coating, qty, price) when
the wizard moves from single-line to header+lines architecture.

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

fusion_plating/fusion_plating_configurator/wizard/__init__.py

@@ -3,4 +3,5 @@
 # License OPL-1 (Odoo Proprietary License v1.0)
 
 from . import fp_direct_order_wizard
+from . import fp_direct_order_line
 from . import fp_part_catalog_import_wizard

fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_line.py

@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+# Part of the Fusion Plating product family.
+
+from odoo import api, fields, models
+
+
+class FpDirectOrderLine(models.TransientModel):
+    _name = 'fp.direct.order.line'
+    _description = 'Fusion Plating - Direct Order Line'
+    _order = 'sequence, id'
+
+    wizard_id = fields.Many2one(
+        'fp.direct.order.wizard',
+        required=True,
+        ondelete='cascade',
+    )
+    sequence = fields.Integer(default=10)
+
+    part_catalog_id = fields.Many2one(
+        'fp.part.catalog',
+        string='Part',
+        required=True,
+    )
+    coating_config_id = fields.Many2one(
+        'fp.coating.config',
+        string='Primary Treatment',
+        required=True,
+    )
+    quantity = fields.Integer(string='Qty', default=1, required=True)
+    currency_id = fields.Many2one(related='wizard_id.currency_id')
+    unit_price = fields.Monetary(
+        string='Unit Price',
+        currency_field='currency_id',
+    )
+    line_subtotal = fields.Monetary(
+        string='Subtotal',
+        currency_field='currency_id',
+        compute='_compute_line_subtotal',
+    )
+
+    @api.depends('quantity', 'unit_price')
+    def _compute_line_subtotal(self):
+        for rec in self:
+            rec.line_subtotal = (rec.quantity or 0) * (rec.unit_price or 0.0)