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.

lib/utils/editor.ts

@@ -0,0 +1,6 @@
+export function convertToHtml(text: string): string {
+    return text
+        .split(/\n\s*\n/)
+        .map((paragraph: string): string => `<p>${paragraph.trim()}</p>`)
+        .join('');
+}