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/globals.css

@@ -24,6 +24,17 @@
   --color-background-light: var(--color-memento-paper);
   --color-background-dark: #202020;
 
+  /* Design tokens from architectural-grid 10 */
+  --color-ink: #1C1C1C;
+  --color-paper: #F2F0E9;
+  --color-muted-ink: rgba(28, 28, 28, 0.6);
+  --color-concrete: #8D8D8D;
+  --color-blueprint: #75B2D6;
+  --color-ochre: #D4A373;
+  --color-sage: #A3B18A;
+  --color-rust: #9B2226;
+  --color-glass: rgba(255, 255, 255, 0.4);
+
   --font-sans: var(--font-inter);
   --font-heading: var(--font-memento-serif), ui-serif, Georgia, "Times New Roman", serif;
   --shadow-level-1: 0 2px 4px rgba(0, 0, 0, 0.04), 0 4px 8px rgba(0, 0, 0, 0.06);