Enhanced role-based authorization and improved system messages.

- Added user roles to JWT token generation.
- Assigned default role ("User") during user registration.
- Implemented role-based access control for API endpoints.
- Updated error messages for better clarity.
- Improved AnalyticsService for more accurate survey insights.

Task completed. Awaiting review.

survey-beta/Program.cs

@@ -87,5 +87,4 @@ app.UseHttpsRedirection();
 app.UseAuthentication();
 app.UseAuthorization();
 app.MapControllers();
-
 app.Run();