New feature - import from CSV

While it's easy to start using the app, new comers usually some with some "baggage" - their past data. So along with the exporting in CSV now each account can import from CSV as well.

Again this happen on the browser, but I was debating to made it through the server side, using AI to detect proper categories and payment types, but then the idea was discarded, as the CSV should be easily formatted to hold proper Categories and receipts.