Add signalement (flag) tags for problem lines on /lignes

New field_flag: free-tagging taxonomy reference (multi-value,
auto-create) on ligne_comptable, for marking a line with an
unstructured problem description (e.g. "client impayé") that can't be
detected automatically the way the répartition écart already is.

- New "Signalement" column, inline-editable like Client/Facture/Libellé
  (comma-separated tags, datalist autocomplete, server-side auto-create
  of unknown tags -- same pattern LedgerActionsController already used
  for Client, now shared via findOrCreateTerm()).
- New "Signalées uniquement" filter, mirroring "Écarts uniquement".
- Flagged rows get a distinct amber left-edge accent (box-shadow, not
  border) so a row that's both in écart and signalée shows both
  indicators without one overwriting the other.
- Native node add/edit form gets the field for free via core's
  entity_reference_autocomplete_tags widget.

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

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

@@ -87,6 +87,14 @@
       <input type="checkbox" v-model="onlyErrors" /> Écarts uniquement
     </label>
 
+    <label class="figli-checkbox">
+      <input type="checkbox" v-model="onlyFlagged" /> Signalées uniquement
+    </label>
+
+    <datalist id="figli-flag-datalist">
+      <option v-for="f in allFlagsList" :key="f" :value="f"></option>
+    </datalist>
+
     <span class="figli-count" v-if="!loading">{{ filteredRows.length }} / {{ rows.length }} lignes chargées{{ errorCount ? ' — ' + errorCount + ' avec écart' : '' }}</span>
   </div>
 
@@ -105,6 +113,7 @@
           <th>Type</th>
           <th>Facture</th>
           <th>Libellé / Détail</th>
+          <th>Signalement</th>
           <th class="amount">Montant HT</th>
           <th class="amount">Montant TTC</th>
           <th v-for="c in allComptes" :key="c" class="amount compte-col">{{ c }}</th>
@@ -113,15 +122,15 @@
       </thead>
       <tbody>
         <tr ref="topSentinel" class="figli-sentinel-row">
-          <td :colspan="7 + allComptes.length + 3">
+          <td :colspan="8 + allComptes.length + 3">
             <span v-if="loadingOlder">Chargement des mois précédents…</span>
           </td>
         </tr>
         <template v-for="item in groupedRows" :key="item.key">
           <tr v-if="item.isGroup" class="figli-group-row" :data-year="item.year">
-            <td :colspan="7 + allComptes.length + 3">{{ item.label }} <span class="figli-note">({{ item.count }} lignes)</span></td>
+            <td :colspan="8 + allComptes.length + 3">{{ item.label }} <span class="figli-note">({{ item.count }} lignes)</span></td>
           </tr>
-          <tr v-else :class="{'figli-error-row': item.hasError}" :data-year="item.date ? item.date.slice(0, 4) : null">
+          <tr v-else :class="{'figli-error-row': item.hasError, 'figli-flag-row': item.hasFlag}" :data-year="item.date ? item.date.slice(0, 4) : null">
             <td class="actions-col">
               <button
                 v-if="item.linkable"
@@ -225,6 +234,23 @@
                 >{{ linkStatus(item).kind === 'ok' ? '' : '⚠ ' }}{{ linkStatusLabel(linkStatus(item)) }}</span>
               </template>
             </td>
+            <td class="figli-flag-cell">
+              <input
+                v-if="isEditingCell(item, 'flag')"
+                v-focus
+                type="text"
+                class="figli-inline-input"
+                list="figli-flag-datalist"
+                :value="item.flags.join(', ')"
+                @change="saveCell(item, 'flag', $event)"
+                @blur="editingCell = null"
+                @keyup.enter="$event.target.blur()"
+              />
+              <span v-else class="figli-editable-cell" title="Cliquer pour signaler un problème" @click="startEditCell(item, 'flag')">
+                <template v-if="item.flags.length"><span v-for="f in item.flags" :key="f" class="figli-flag-badge">{{ f }}</span></template>
+                <template v-else>—</template>
+              </span>
+            </td>
             <td class="amount" :class="montantClass(item.montant_ht)">{{ formatEur(item.montant_ht) }}</td>
             <td class="amount">{{ formatEur(item.montant_ttc) }}</td>
             <td v-for="c in allComptes" :key="c" class="amount compte-col">{{ item.parCompte[c] !== undefined ? formatEur(item.parCompte[c]) : '' }}</td>
@@ -232,7 +258,7 @@
           </tr>
         </template>
         <tr ref="bottomSentinel" class="figli-sentinel-row">
-          <td :colspan="7 + allComptes.length + 3">
+          <td :colspan="8 + allComptes.length + 3">
             <span v-if="loadingNewer">Chargement des mois suivants…</span>
           </td>
         </tr>
@@ -241,7 +267,7 @@
         <tr class="figli-totals-row">
           <td class="actions-col"></td>
           <td class="actions-col"></td>
-          <td colspan="5">
+          <td colspan="6">
             Solde {{ currentYear || '…' }} (créditeur / débiteur)
             <span v-if="currentYearLoading" class="figli-note">chargement…</span>
           </td>