Allow selecting several comptes/types at once in the filters

Compte and Type were single-value <select> elements. Converted both to
<select multiple> -- Vue binds those to an array natively, so
ctrl/cmd+click and shift+click just work with no custom JS. Matching
semantics are OR within a filter (any of the selected comptes/types) and
AND across filters, same as the existing client/year/écarts filters.

The URL hash (compte=Maud,Bachir&type=versement,achat) now carries
comma-separated lists instead of a single value, so the shareable/
reloadable filtered view still works with multiple selections.

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

@@ -20,8 +20,7 @@
     {% verbatim %}
 
     <label>Compte
-      <select v-model="filterCompte">
-        <option value="">Tous</option>
+      <select v-model="filterCompte" multiple size="4" title="Ctrl/Cmd+clic ou Maj+clic pour plusieurs comptes">
         <option v-for="c in allComptes" :key="c" :value="c">{{ c }}</option>
       </select>
     </label>
@@ -34,8 +33,7 @@
     </label>
 
     <label>Type
-      <select v-model="filterType">
-        <option value="">Tous</option>
+      <select v-model="filterType" multiple size="4" title="Ctrl/Cmd+clic ou Maj+clic pour plusieurs types">
         <option v-for="t in allTypes" :key="t.value" :value="t.value">{{ t.label }}</option>
       </select>
     </label>