Remove unused components and models for improved maintainability

- Deleted redundant components (`AddActionButton`, `AlertBox`, `AlertStack`, `BackButton`, `CancelButton`, and `CollapsableArea`) and related files.
- Removed unused models (`Book`, `BookSerie`, `BookTables`, `Character`, and `Chapter`) to reduce codebase clutter.
- Updated project structure and references to reflect these removals.

context/AlertProvider.tsx

@@ -2,8 +2,7 @@
 
 import type {Context, Dispatch, JSX, ReactNode, SetStateAction} from 'react';
 import React, {createContext, useCallback, useState} from 'react';
-import AlertStack from '@/components/AlertStack';
-import {cleanErrorMessage} from '@/lib/errors';
+import AlertStack from '@/components/ui/AlertStack';
 
 export type AlertType = 'success' | 'error' | 'info' | 'warning';