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.

components/form/DatePicker.tsx

@@ -1,4 +1,4 @@
-import {ChangeEvent} from "react";
+import React, {ChangeEvent} from "react";
 
 interface DatePickerProps {
     date: string;
@@ -15,7 +15,7 @@ export default function DatePicker(
             type="date"
             value={date}
             onChange={setDate}
-            className="bg-secondary/50 text-text-primary px-4 py-2.5 rounded-xl border border-secondary/50 focus:border-primary focus:ring-4 focus:ring-primary/20 focus:bg-secondary hover:bg-secondary hover:border-secondary outline-none transition-all duration-200"
+            className="input-base"
         />
     )
 }