[#22] Auto-upload entered text before submitting a search request

This PR changes the upload text popup behavior such that, when pressing the Search button before submitting the text, the text is first uploaded and the embeddings are then passed to the search request.

Also, the entered text, if not uploaded yet, is saved in local storage so that it remains available when the page reloads, and will remain visible when opening the Upload popup. The next time the Search button is pressed, the text will be uploaded automatically before the search request.