Fix empty Facture/Libellé cells having nothing to click

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.

web/modules/custom/figli_compta_ledger/templates/figli-compta-home.html.twig

@@ -185,7 +185,7 @@
                 @blur="editingCell = null"
                 @keyup.enter="$event.target.blur()"
               />
-              <span v-else class="figli-editable-cell" title="Cliquer pour modifier" @click="startEditCell(item, 'facture')">{{ item.facture }}</span>
+              <span v-else class="figli-editable-cell" title="Cliquer pour modifier" @click="startEditCell(item, 'facture')">{{ item.facture || '—' }}</span>
             </td>
             <td class="figli-libelle">
               <input
@@ -198,7 +198,7 @@
                 @keyup.enter="$event.target.blur()"
               />
               <template v-else>
-                <span class="figli-editable-cell" title="Cliquer pour modifier" @click="startEditCell(item, 'libelle')">{{ item.libelle }}</span>
+                <span class="figli-editable-cell" title="Cliquer pour modifier" @click="startEditCell(item, 'libelle')">{{ item.libelle || '—' }}</span>
                 <span
                   v-if="item.type === 'entree' && reconciliationByEntree.get(item.id) && reconciliationByEntree.get(item.id).count > 0"
                   class="figli-recon-badge is-clickable"