feat(dashboard): tableau de bord Second Brain configurable avec chargement progressif

Briefing granulaire, pistes rapides puis enrichissement async, layout persisté v5,
suggestions agents, intégration Gmail et navigation sidebar alignée sur /home.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/components/organize-notebook-dialog.tsx

@@ -42,7 +42,7 @@ export function OrganizeNotebookDialog({
   const handleAnalyze = useCallback(async () => {
     setStep('analyzing'); setError(null); setPlan(null)
     const res = await analyzeNotebookForOrganization(notebookId, language)
-    if (!res.success || !res.plan) { setError(res.error ?? 'Erreur'); setStep('idle'); return }
+    if (!res.success || !res.plan) { setError(res.error ?? t('common.error')); setStep('idle'); return }
     setPlan(res.plan)
     setEditableGroups(res.plan.groups.map(g => ({ ...g, notes: [...g.notes] })))
     setExpandedGroups(new Set(res.plan.groups.map((_, i) => i)))
@@ -74,7 +74,7 @@ export function OrganizeNotebookDialog({
       groups: editableGroups.filter(g => g.notes.length > 0 && g.name.trim()),
     }
     const res = await executeNotebookOrganization(finalPlan)
-    if (!res.success) { setError(res.error ?? 'Erreur'); setStep('preview'); return }
+    if (!res.success) { setError(res.error ?? t('common.error')); setStep('preview'); return }
     setResult({ created: res.created, moved: res.moved })
     setStep('done')
     toast.success(t('organizeNotebook.toastSuccess', { created: res.created, moved: res.moved }))