[FIX] product_replenishment_cost: skip currency convert when same currency in compute

_compute_price_unit_and_date_planned_and_name was calling _convert()
unconditionally, which applies currency rounding even for same-currency
pairs. For supplier prices below currency precision (e.g. 0.0046 USD
rounded to 2 decimals = 0.00), this caused price_unit to compute as 0
on manually added PO lines.

_prepare_purchase_order_line already guards with
  if supplier.currency_id != po.currency_id
Apply the same guard in the compute method.

Author: Juan Ignacio Carreras

product_replenishment_cost/__manifest__.py

@@ -1,6 +1,6 @@
 {
     "name": "Replenishment Cost",
-    "version": "18.0.1.1.0",
+    "version": "18.0.1.2.0",
     "author": "ADHOC SA, Odoo Community Association (OCA)",
     "license": "AGPL-3",
     "category": "Products",

product_replenishment_cost/models/purchase_order_line.py

@@ -33,9 +33,10 @@ def _compute_price_unit_and_date_planned_and_name(self):
                 if seller
                 else 0.0
             )
-            price_unit = seller.currency_id._convert(
-                price_unit, line.currency_id, line.company_id, line.date_order or fields.Date.today()
-            )
+            if seller.currency_id and line.currency_id and seller.currency_id != line.currency_id:
+                price_unit = seller.currency_id._convert(
+                    price_unit, line.currency_id, line.company_id, line.date_order or fields.Date.today()
+                )
 
             if seller and line.product_uom and seller.product_uom != line.product_uom:
                 price_unit = seller.product_uom._compute_price(price_unit, line.product_uom)