Team login / logout

When a teammate's online state flips, the bot can post:

• "<name> just logged in."
• "<name> just logged out."

Both are independently toggleable in Settings — login and logout are separate switches, so you can have one on and the other off (most teams keep login on for "raid window opened?" awareness, but logout off because it spams during sleep waves).

The dashboard's Team roster page always shows the current online/offline state regardless of the chat toggle, with a small uptime indicator next to each name.