Facture and libellé rendered their span with no fallback text when
empty, unlike Client's existing "|| '—'" -- an empty span has zero
width/height, so there was nothing there to click at all. Added the
same "—" placeholder to both.
Also switched .figli-editable-cell to display: block with a min-height,
so the clickable area fills the whole cell's content box instead of
just hugging the text -- a lone "—" character was still a tiny target
even with a placeholder.