fix: remove completed and expired votekick entries from votekickList

[xpoes123]

Completed and abandoned votekick entries were never removed from votekickList in ServerMultiplayerRoomMixin.js, causing two distinct problems: the list grew without bound in long-lived rooms (slow memory leak), and a successful or expired votekick permanently blocked any future votekick against the same user until the server restarted.

Problem

votekickInit short-circuits if an entry for the target already exists:

if (this.votekickList.find(vk => vk.exists(targetId))) { return; }

Because entries were never pruned, a completed kick — or one that simply expired — would prevent any re-initiation for that user for the lifetime of the server process. In rooms with heavy moderation activity, the list also accumulated unboundedly.

Changes

• Adds this.createdAt = Date.now() to the Votekick constructor (VoteKick.js) so entries carry a timestamp.
• Removes a target's entry from votekickList on the successful check() branch in both votekickInit and votekickVote, so a re-initiation is possible if the user rejoins after being kicked.
• Prunes stale entries inside the existing cleanupExpiredBansAndKicks method using BAN_DURATION as the TTL, consistent with how bans and kicks are already expired.

Risk & testing

In-progress votes are never disrupted: entries are only removed on success or after the TTL window has passed. The cleanupExpiredBansAndKicks pruning is additive — the surrounding ban/kick cleanup is unchanged. semistandard and node --check pass.