[SignInPage] Allow modifying session using setSession

[aress31]

• From user pain:

I believe that useSession should return both session and setSession. In many parts of an application, such as the SignInPage, a successful sign-in requires setting the session. Currently, this can only be done at the top level in the AppProvider, forcing the setter to be passed down multiple levels through the component hierarchy. Allowing this hook to both read and update the session directly would significantly expand its usability across various use cases.