Added function - Asynchronous import

Now Hotlist.biz has implemented asynchronous product import — this means that you can upload large volumes of data without refreshing the page and without temporary site downtime for you.
🔹 Previously: during import, the site became temporarily unavailable to the administrator until the entire process was completed. This was inconvenient — especially with a large number of products.
🔹 Now: you can continue working with the site while the import runs in the background. The import process no longer blocks the interface, and lines from the file are processed and displayed in real time directly on the screen.
💡 For example, when uploading 5000 products, each containing dozens of images, processing time can take tens of minutes. Asynchronous import completely solves this problem — the site remains accessible, and you see the progress.

You can enable the "Asynchronous Import" option to upload large volumes of data in the background.

Advantages:

Import runs in the background — you can continue working with the site during processing.
The browser is not overloaded, and you see progress in real time.

Important:

If you do not use asynchronous mode, the site will become temporarily unavailable specifically for you during the import. However, for other users, it will continue to work normally.
During asynchronous import, a detailed log for each product is not available — you will not see which specific fields were changed for each item in real time.
After the import is completed, a brief summary report will be available with a list of updated, skipped, deleted, and problematic products and variations.
History is available under "Show previous import result" or "Previous import process".

Added "Purchase price" for varieties.
Updated the layout for the display of the 'Add to Cart' button.
Added "Quick import" of collections.