Refine transaction amount parsing in mock server:

- Ensure amounts include the ₽ currency symbol for accurate parsing.

tests/mock_server/gen_fetch_transactions.py

@@ -230,7 +230,7 @@ def parse_ozon_rows(xml):
             continue
         if "Расход" in text or "Доход" in text:
             continue
-        am = re.search(r"([+\-−])\s*(\d[\d\s\u202f]*(?:[,.]\d{1,2})?)", text)
+        am = re.search(r"([+\-−])\s*(\d[\d\s\u202f]*(?:[,.]\d{1,2})?)\s*₽", text)
         if not am:
             continue
         sign = -1 if am.group(1) in ("-", "−") else 1