fix: honor PayKilla invoice currency

backend/bot/payment_providers/paykilla.py

@@ -396,7 +396,7 @@ class PaykillaService(HttpClientMixin):
 
     @property
     def currency(self) -> str:
-        return (self.config.CURRENCY or "RUB").upper()
+        return normalize_payment_currency_code(self.config.CURRENCY or "RUB")
 
     @property
     def verify_webhook_signature(self) -> bool:
@@ -416,7 +416,7 @@ class PaykillaService(HttpClientMixin):
         currency: Optional[str],
         description: str,
     ) -> Dict[str, Any]:
-        currency_code = normalize_payment_currency_code(currency or self.currency)
+        currency_code = self.currency
         invoice_text = _invoice_text(getattr(self.settings, "WEBAPP_TITLE", None), payment_db_id)
         body: Dict[str, Any] = {
             "type": _invoice_type_for(self.config, currency_code),
@@ -449,7 +449,8 @@ class PaykillaService(HttpClientMixin):
             logging.error("PaykillaService is not configured. Cannot create payment link.")
             return False, {"message": "service_not_configured"}
 
-        currency_code = normalize_payment_currency_code(currency or self.currency)
+        payment_currency = normalize_payment_currency_code(currency or self.currency)
+        currency_code = self.currency
         supported = parse_supported_currency_codes(self.config.SUPPORTED_CURRENCIES)
         if supported and currency_code not in supported:
             return False, {
@@ -457,6 +458,13 @@ class PaykillaService(HttpClientMixin):
                 "currency": currency_code,
                 "supported_currencies": list(supported),
             }
+        if payment_currency and payment_currency != currency_code:
+            logging.info(
+                "Paykilla create_payment_link: using configured invoice currency %s "
+                "instead of payment record currency %s; amount is sent unchanged.",
+                currency_code,
+                payment_currency,
+            )
 
         body = self._invoice_body(
             payment_db_id=payment_db_id,
@@ -986,7 +994,8 @@ _CONFIG_MANIFEST = (
         "string",
         "Invoice currency",
         description=(
-            "Fiat or crypto invoice currency. FIAT_BASED is selected for RUB/USD/EUR/AED/GBP."
+            "PayKilla invoice currency. Amount is sent unchanged, so keep tariffs "
+            "priced in this currency or use a PayKilla-enabled fiat such as USD."
         ),
         placeholder="RUB",
         subsection="PayKilla",