Update to v3 of Flask

[asrashley]

The current version of Flask is v3.0.3, but this code uses v2.3.3

To be able to update Flask will also require other libraries to be updated

    The user requested Flask==3.0.3
    flask-socketio 5.3.6 depends on Flask>=0.9
    flask-sqlalchemy 3.0.3 depends on Flask>=2.2
    flask-jwt-extended 4.5.2 depends on Flask<3.0 and >=2.0