[accessibility] files: invisible but focusable element between "new"-button and "switch to grid view"-button

Current state: There is an invisible but focusable element between the "New" and "Tile/List View" buttons. Keyboard users have to take an extra tab step, without any visible or usable control. Screen readers announce content that is not visually present ("Browse…").

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This element is the `<input>` field of the uploader component.