Consecutive file uploads should not show previous selections by default

[thorwhalen]

If I want to upload a new batch, it's quite annoying to have the previous selection "stick" like it does.
Especially when there's a lot of files to "deselect".

Perhaps a button to clear this selection could also be a solution? A better one?

┆Issue is synchronized with this Asana task by Unito

(This comes from the app described here).

[thorwhalen]

Likely out of scope for this repo: `front/elements/elements.py::FileUploaderBase` is the backend-agnostic specification of a file-upload input (type restriction, `accept_multiple_files` flag) -- it has no rendering/state-reset logic itself. The "previous selection sticks between uploads" behavior this issue reports would be implemented in the concrete Streamlit renderer (`streamlitfront`, a separate downstream repo), which I didn't cross into for this pass. Recommend re-filing or cross-linking there if not already tracked; leaving open here since I can't confirm either way from this repo alone.