UI Stabilization: Global color theme updates (#75B2D6), AI Assistant styling refactor, and navigation fixes

memento-note/lib/types.ts

@@ -28,6 +28,7 @@ export interface Label {
   id: string;
   name: string;
   color: LabelColorName;
+  type?: 'ai' | 'user';  // "ai" for auto-generated, "user" for manually created
   notebookId: string | null; // NEW: Belongs to a notebook
   userId?: string | null; // DEPRECATED: Kept for backward compatibility
   createdAt: Date;