Sessions ERM Parity

Sessions now match ERM's vote, start, boost, info and end flow while keeping Vex extras like schedules, locks, auto-kick and auto-end.

New and updated: /session vote, /session poll with required votes and staff only polls, a View Votes button, /session boost, /session info with peak players, mod calls and a graph, /session autostart, /session embed set staff_poll and a richer /session history.

/import now brings ERM session settings and history into Vex, and startup embeds with {players} refresh live while a session is running.