Feature Request: Add User Authentication

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## Overview

Currently, the TaskManager application does not support user authentication, which could lead to unauthorized access to project data. Implementing an authentication system would enhance security and allow for a more personalized experience for users.

## Proposed Solution

- Integrate a user authentication mechanism using either JWT (JSON Web Tokens) or OAuth.
- Create user registration and login forms in AngularJS.
- Protect sensitive routes on the back-end to ensure only authenticated users can access or modify tasks.

## Benefits
- Improved security for project data.
- Ability to manage user roles and permissions.
- Increased user trust and satisfaction with the application.

## Additional Context
Consider using existing libraries such as ASP.NET Identity for the C# backend and Auth0 or Firebase for the frontend authentication to streamline the implementation process.

Start by mapping the AngularJS registration and login forms to the C# backend routes that handle project data. Compare the proposed JWT, OAuth, ASP.NET Identity, Auth0, and Firebase options before choosing an approach. Done means users can register and log in, sensitive routes reject unauthenticated access, and roles and permissions are handled.

Written by the indexing model from the issue text.