Activity and Sub-Activity Management System Integration for Existing Administrative Application

I need enhancements made to an existing administrative management application while preserving all current features, files, database structures, permissions, reports, interfaces, and business logic. No existing functionality should be removed, simplified, or altered.

The main requirement is to implement a complete Activity and Sub-Activity Management system integrated into the existing application.

Requirements:

Add a new button on the main interface called "Activity Management" next to the "Employee Management" button.
Create a dedicated window for managing Activities and Sub-Activities.
Allow administrators to add, edit, delete, and search Activities.
Allow administrators to add, edit, delete, and search Sub-Activities linked to their parent Activities.
Store all changes directly in the database.
Automatically synchronize Activities and Sub-Activities with all dropdown lists, forms, and input fields throughout the application.
Automatically integrate new Activities and Sub-Activities into the main data table, data entry forms, edit forms, search functions, reports, statistics, exports, and printing features.
Ensure that any changes are reflected immediately throughout the system without requiring application restarts.
Prevent duplicate records and maintain database integrity and relationships between Activities and Sub-Activities.
Respect the existing permissions system so that only Admin users can create, modify, or delete Activities and Sub-Activities, while standard users can only use existing records.

Important constraints:

Do not remove any existing code.
Do not delete any files.
Do not modify existing working functionality.
Do not change the current user interface design except for the additions required by this feature.
Do not remove any reports, permissions, tables, or existing business logic.
Maintain full backward compatibility with existing data and system behavior.

Expected deliverables:

Updated database structure if required.
New "Activity Management" button on the main interface.
Complete Activity and Sub-Activity Management window.
Full CRUD functionality (Create, Read, Update, Delete).
Search and filtering capabilities.
Automatic integration with all relevant parts of the application.
Updated source code with all modifications properly integrated.
A fully functional version of the application with all original and new features working correctly.