Initial Drupal site: content model + validation + Vue dashboard

- Content type "Ligne comptable" with Paragraphs "Répartition" (Compte + Montant)
- Taxonomies: Compte (9 comptes) and Client (unified client list)
- hook_node_presave + form validate: sum(répartition) must equal montant HT
- /dashboard route (progressive decoupling): Vue 3 app fetching JSON:API,
  computing solde par compte / par client client-side
- "Ajouter une ligne" opens the real Drupal node form in an AJAX modal
- Gin as default + admin theme
- 9 opening-balance lines seeded from suivi_compta_SASFigli2026_v2.ods

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

.gitignore

@@ -0,0 +1,8 @@
+/vendor/
+/web/core/
+/web/modules/contrib/
+/web/themes/contrib/
+/web/libraries/
+/web/sites/*/files/
+/web/sites/*/settings.local.php
+.env