feat: hierarchical notebook system - trash, selectors, breadcrumb, sidebar tree

- Schema: soft delete with trashedAt on Notebook model
- API: PATCH/GET notebooks support trashedAt filtering with cascade
- Sidebar: recursive tree rendering with collapse/expand, visual guides, hover actions
- HierarchicalNotebookSelector: portal-based dropdown with search, breadcrumbs, dropUp support
- AI chat: context selector with Toutes mes notes + notebook selector
- Agent detail: flat selects replaced with HierarchicalNotebookSelector
- Breadcrumb: notebook path display on home page
- Trash view: card grid with countdown, restore/permanent delete
- CSS: design tokens (ink, paper, blueprint, concrete, etc.)
- Types: parentId, trashedAt added to Notebook interface

memento-note/app/api/notebooks/route.ts

@@ -31,7 +31,7 @@ export async function GET(request: NextRequest) {
 
   try {
     const notebooks = await prisma.notebook.findMany({
-      where: { userId: session.user.id },
+      where: { userId: session.user.id, trashedAt: null },
       include: {
         labels: { orderBy: { name: 'asc' } },
         _count: {