feat: hierarchical notebooks (tree), remove all list view code, delete 22 unused files

- Add parentId to Notebook model (tree structure)
- Update sidebar to render parent/child notebooks with expand/collapse
- Add sub-notebook creation from parent notebook
- Remove 'list' from NotesViewMode type everywhere
- Delete 22 unused components, hooks, and UI files
- Wrap revalidatePath in try-catch to prevent save 500
- Update notebook API to support parentId in creation

memento-note/app/actions/ai-settings.ts

@@ -14,7 +14,7 @@ export type UserAISettingsData = {
   preferredLanguage?: 'auto' | 'en' | 'fr' | 'es' | 'de' | 'fa' | 'it' | 'pt' | 'ru' | 'zh' | 'ja' | 'ko' | 'ar' | 'hi' | 'nl' | 'pl'
   demoMode?: boolean
   showRecentNotes?: boolean
-  notesViewMode?: 'masonry' | 'tabs' | 'list'
+  notesViewMode?: 'masonry' | 'tabs'
   emailNotifications?: boolean
   desktopNotifications?: boolean
   anonymousAnalytics?: boolean
@@ -64,8 +64,7 @@ function pickUserAISettingsForDb(input: UserAISettingsData): Partial<Record<User
   if (
     out.notesViewMode != null &&
     out.notesViewMode !== 'masonry' &&
-    out.notesViewMode !== 'tabs' &&
-    out.notesViewMode !== 'list'
+    out.notesViewMode !== 'tabs'
   ) {
     delete out.notesViewMode
   }
@@ -170,9 +169,7 @@ const getCachedAISettings = unstable_cache(
           ? ('masonry' as const)
           : raw === 'tabs'
             ? ('tabs' as const)
-            : raw === 'list'
-              ? ('list' as const)
-              : ('masonry' as const)
+            : ('masonry' as const)
 
       return {
         titleSuggestions: settings.titleSuggestions,