chore: rewrite user-facing messages in Subcontracting module

Conservative cleanup of frappe.throw/msgprint messages per the message style
guide; meaning, severity, and .format() arguments are unchanged:

- index bare {} placeholders as {0}/{1}/... so translators can reorder
- move f-strings / .format() / concatenation out of _() (they break gettext
  extraction and never translate)
- wrap translatable dynamic values (DocType/Select labels) in _()
- fix grammar and colloquialisms
- drop no-op _() wrapping runtime-built strings

Part of #53976.

erpnext/subcontracting/doctype/subcontracting_inward_order/subcontracting_inward_order.py

@@ -224,7 +224,7 @@ class SubcontractingInwardOrder(SubcontractingController):
 			if not any([rm.is_customer_provided_item for rm in raw_materials]):
 				frappe.throw(
 					_(
-						"Atleast one raw material for Finished Good Item {0} should be customer provided."
+						"At least one raw material for Finished Good Item {0} should be customer provided."
 					).format(frappe.bold(item.item_code))
 				)
 

erpnext/subcontracting/doctype/subcontracting_order/subcontracting_order.py

@@ -139,12 +139,14 @@ class SubcontractingOrder(SubcontractingController):
 				frappe.throw(_("Please select a valid Purchase Order that is configured for Subcontracting."))
 
 			if po.docstatus != 1:
-				msg = f"Please submit Purchase Order {po.name} before proceeding."
-				frappe.throw(_(msg))
+				frappe.throw(_("Please submit Purchase Order {0} before proceeding.").format(po.name))
 
 			if po.per_received == 100:
-				msg = f"Cannot create more Subcontracting Orders against the Purchase Order {po.name}."
-				frappe.throw(_(msg))
+				frappe.throw(
+					_("Cannot create more Subcontracting Orders against the Purchase Order {0}.").format(
+						po.name
+					)
+				)
 		else:
 			self.service_items = self.items = self.supplied_items = None
 			frappe.throw(_("Please select a Subcontracting Purchase Order."))
@@ -172,8 +174,11 @@ class SubcontractingOrder(SubcontractingController):
 		if self.supplier_warehouse:
 			for item in self.supplied_items:
 				if self.supplier_warehouse == item.reserve_warehouse:
-					msg = f"Reserve Warehouse must be different from Supplier Warehouse for Supplied Item {item.main_item_code}."
-					frappe.throw(_(msg))
+					frappe.throw(
+						_(
+							"Reserve Warehouse must be different from Supplier Warehouse for Supplied Item {0}."
+						).format(item.main_item_code)
+					)
 
 	def set_missing_values(self):
 		self.calculate_additional_costs()

erpnext/subcontracting/doctype/subcontracting_receipt/subcontracting_receipt.py

@@ -143,7 +143,7 @@ class SubcontractingReceipt(SubcontractingController):
 			self.validate_inspection()
 
 		if getdate(self.posting_date) > getdate(nowdate()):
-			frappe.throw(_("Posting Date cannot be future date"))
+			frappe.throw(_("Posting Date cannot be a future date"))
 
 		super().validate()