Fix PlayFab credential refresh

[Maryam (maryammadzadeh)]

I rechecked the PlayFab authentication flow and found two related issues:

• New users ignore the token expiration returned by PlayFab and always schedule authentication after 12 hours.
• When an existing user refreshes expired credentials, only the Party token is updated. PFMultiplayer keeps the expired entity token, and the cached session ticket also remains stale.
• This proposal uses the server’s HTTP Date header with TokenExpiration to calculate the token lifetime without relying on the client clock. It refreshes halfway through that lifetime and updates Party, PFMultiplayer, and the cached session ticket together.