Add solde totals footer row + fix JSON:API pagination duplicate bug

- tfoot row: sum per compte (créditeur/débiteur colored) for the
  currently filtered rows, plus HT/TTC/écart totals
- Fixed a real bug: fetchAllLignes() paginated without a unique sort key
  (field_date_ligne alone, many ties), which let Drupal's JSON:API return
  the same row on two pages -- silently inflating totals (Bachir showed
  -3115,38€ instead of -3013,56€). Now sorts by
  field_date_ligne,drupal_internal__nid (home) / drupal_internal__nid
  (dashboard), plus a defensive client-side de-dup by node id either way.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

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

@@ -86,6 +86,15 @@
           </tr>
         </template>
       </tbody>
+      <tfoot>
+        <tr class="figli-totals-row">
+          <td colspan="4">Solde (créditeur / débiteur) — {{ filteredRows.length }} lignes filtrées</td>
+          <td class="amount">{{ formatEur(footerTotals.montant_ht) }}</td>
+          <td class="amount">{{ formatEur(footerTotals.montant_ttc) }}</td>
+          <td v-for="c in allComptes" :key="c" class="amount compte-col" :class="soldeClass(footerTotals.parCompte[c])">{{ formatEur(footerTotals.parCompte[c]) }}</td>
+          <td class="amount" :class="soldeClass(footerTotals.ecart)">{{ formatEur(footerTotals.ecart) }}</td>
+        </tr>
+      </tfoot>
     </table>
   </div>
 </div>