audit week 1: creator ID tracking, channel-queue migration, deprecation cleanup

QUAL-006  store ticket.creatorId on creation; legacy split-pop returned the
          message ID for discord-msg-* tickets, breaking transcript DM, close
          log, and channel rename for context-menu-created tickets. Adds the
          field to the Ticket schema and writes a one-shot backfill script
          (scripts/backfill-creatorId.js, dry-run by default).

QUEUE-001 add enqueueOverwrite + enqueueTopic to services/channelQueue.js
          (chain on renameChains alongside enqueueMove). Migrate handleAdd /
          handleRemove / handleMove / handleTopic so permissionOverwrites,
          setParent, and setTopic no longer race pending renames or sends.
          handleMove now uses the existing enqueueMove. Initial overwrites in
          handleTicketModal stay inline; channel doesn't exist yet so no race.

DISCORD-001 replace ephemeral: true with flags: MessageFlags.Ephemeral across
            broccolini-discord.js, handlers/sharedHelpers.js, handlers/buttons.js,
            handlers/commands.js. runDeferred opts now take { flags } directly.

SEC-003   /gmailpoll min interval is 30s. Drop the 5s/10s slash-command
          choices and clamp Math.max(30000, ms) in handleGmailPoll for
          defense in depth.

QUAL-001  upgrade silent .catch(() => {}) on the lastActivity updateOne in
          handlers/messages.js to log via logError, so transient Mongo errors
          surface in the debug channel instead of disappearing.

QUAL-002  drop await from logError/logWarn calls in services/staffThread.js
          and services/pinMessage.js — fire-and-forget per CLAUDE.md hard rule.

QUAL-003  wrap stray setTimeouts (handleConfirmCloseRequest force-close timer,
          runFinalClose channel-delete + overflow-cleanup, checkAutoClose
          delete-after-email) in trackTimeout via lazy require so they clear
          on shutdown.

commands/register.js

@@ -357,8 +357,6 @@ async function registerCommands() {
           .setDescription('Poll interval')
           .setRequired(true)
           .addChoices(
-            { name: '5s', value: '5' },
-            { name: '10s', value: '10' },
             { name: '30s', value: '30' },
             { name: '45s', value: '45' },
             { name: '1m', value: '60' },