feat(auth): Implement route guards for authentication

[Zafar7645]

User Story: As an application, I want to protect private routes so that only authenticated users can access them.

Acceptance Criteria:

• Create an AuthGuard in the Angular application.
• The guard should check for the presence and validity of the JWT.
• If the user is authenticated, allow access to the requested route.
• If the user is not authenticated, redirect them to the /login page.
• Apply this guard to all private routes, such as the main dashboard and project views.
• On the backend, create a guard to protect all private API endpoints, validating the JWT sent in the request headers.