feat(selling): add proforma invoice settings and tracking field

- Selling Settings: "Enable Proforma Invoice" toggle (opt-in) and a
  default proforma print format
- Sales Order Item: non-blocking proforma_qty counter

erpnext/selling/doctype/sales_order_item/sales_order_item.json

@@ -102,6 +102,7 @@
   "column_break_69",
   "work_order_qty",
   "delivered_qty",
+  "proforma_qty",
   "produced_qty",
   "returned_qty",
   "picked_qty",
@@ -702,6 +703,14 @@
    "read_only": 1,
    "width": "100px"
   },
+  {
+   "fieldname": "proforma_qty",
+   "fieldtype": "Float",
+   "label": "Proforma Qty",
+   "no_copy": 1,
+   "print_hide": 1,
+   "read_only": 1
+  },
   {
    "fieldname": "work_order_qty",
    "fieldtype": "Float",

erpnext/selling/doctype/sales_order_item/sales_order_item.py

@@ -71,6 +71,7 @@ class SalesOrderItem(Document):
 		price_list_rate: DF.Currency
 		pricing_rules: DF.SmallText | None
 		produced_qty: DF.Float
+		proforma_qty: DF.Float
 		production_plan_qty: DF.Float
 		project: DF.Link | None
 		projected_qty: DF.Float

erpnext/selling/doctype/selling_settings/selling_settings.json

@@ -60,6 +60,9 @@
   "allow_delivery_of_overproduced_qty",
   "column_break_mla9",
   "deliver_secondary_items",
+  "proforma_invoice_section",
+  "enable_proforma_invoice",
+  "default_proforma_print_format",
   "default_naming_tab",
   "transaction_naming_html"
  ],
@@ -341,6 +344,26 @@
    "fieldtype": "Check",
    "label": "Deliver secondary Items"
   },
+  {
+   "fieldname": "proforma_invoice_section",
+   "fieldtype": "Section Break",
+   "label": "Proforma Invoice"
+  },
+  {
+   "default": "0",
+   "description": "Allow issuing Proforma Invoices against a Sales Order.",
+   "fieldname": "enable_proforma_invoice",
+   "fieldtype": "Check",
+   "label": "Enable Proforma Invoice"
+  },
+  {
+   "depends_on": "enable_proforma_invoice",
+   "description": "Default print format used when generating a Proforma Invoice PDF.",
+   "fieldname": "default_proforma_print_format",
+   "fieldtype": "Link",
+   "label": "Default Proforma Print Format",
+   "options": "Print Format"
+  },
   {
    "fieldname": "customer_defaults_tab",
    "fieldtype": "Tab Break",

erpnext/selling/doctype/selling_settings/selling_settings.py

@@ -41,6 +41,7 @@ class SellingSettings(Document):
 		blanket_order_allowance: DF.Float
 		cust_master_name: DF.Literal["Customer Name", "Naming Series", "Auto Name"]
 		customer_group: DF.Link | None
+		default_proforma_print_format: DF.Link | None
 		deliver_secondary_items: DF.Check
 		dn_required: DF.Literal["No", "Yes"]
 		dont_reserve_sales_order_qty_on_sales_return: DF.Check
@@ -48,6 +49,7 @@ class SellingSettings(Document):
 		editable_price_list_rate: DF.Check
 		enable_cutoff_date_on_bulk_delivery_note_creation: DF.Check
 		enable_discount_accounting: DF.Check
+		enable_proforma_invoice: DF.Check
 		enable_tracking_sales_commissions: DF.Check
 		enable_utm: DF.Check
 		fallback_to_default_price_list: DF.Check