v0.9.1 - Voice channel awareness

Voice channel features

• VC status now auto-clears after a game has actually been played: once the creator has been in the voice
  channel for 10+ minutes and the channel later empties, the status is silently cleared.
• Posts where the creator + at least one other player spent 1+ hour together in the VC now expire after 3
  hours instead of the default 12.
• VC status output simplified: just PvP - description (the slot count (N/M) was redundant with the post
  embed).

Embed

• Empty party slots now render as 2. _______ placeholders instead of "Empty", so the slot layout is visible
  at a glance.

Correctness

• One active LFG post per voice channel is now enforced at creation and on ChangeVC -- prevents two parties
  accidentally claiming the same VC.
• In-memory VC tracking state is now purged when posts are closed manually or by cleanup.
• Removed an unused get_lfg_members fetch from update_vc_status (called on every join/leave).

Docs

• README updated to describe the VC-aware cleanup behavior.