/transfer: validate target via isStaff() — covers ADDITIONAL_STAFF_ROLES

The transfer-target check previously matched only against
CONFIG.ROLE_TO_PING_ID, so a member with one of
CONFIG.ADDITIONAL_STAFF_ROLES (a recognized staff role everywhere else
in the bot, including requireStaffRole and the messages.js claimer-DM
path) was rejected as a transfer target. Switch to isStaff() so the
transfer-target gate matches the rest of the codebase's staff
definition.

Also:
- Reject bots as transfer targets (guildMember.user.bot).
- Reject self-transfer (transferring to interaction.user.id) — the
  rename + DB write would no-op but the log line claimed a transfer
  that didn't happen.
- Resolve the target member cache-first to avoid an unnecessary REST
  round-trip when the GuildMembers intent has the user cached.

handlers/commands/index.js

@@ -17,6 +17,7 @@
 const { EmbedBuilder, MessageFlags } = require('discord.js');
 const { mongoose } = require('../../db-connection');
 const { CONFIG } = require('../../config');
+const { isStaff } = require('../../utils');
 const { setNotifyDm } = require('../../services/staffSettings');
 const { makeTicketName, resolveCreatorNickname } = require('../../services/tickets');
 const { enqueueRename, enqueueMove, enqueueOverwrite, enqueueTopic, enqueueSend } = require('../../services/channelQueue');
@@ -95,11 +96,26 @@ async function handleTransfer(interaction) {
   const ticket = await findTicketForChannel(interaction);
   if (!ticket) return;
 
-  const staffRoleId = CONFIG.ROLE_TO_PING_ID;
-  const guildMember = await interaction.guild.members.fetch(member.id).catch(() => null);
+  // Cache-first member resolution; falls back to a fetch if not in cache.
+  // GuildMembers intent keeps the cache warm in normal operation.
+  const guildMember = interaction.guild.members.cache.get(member.id)
+    || await interaction.guild.members.fetch(member.id).catch(() => null);
 
-  if (!guildMember || !guildMember.roles.cache.has(staffRoleId)) {
-    return interaction.reply({ content: 'The target member must have the staff role.', flags: MessageFlags.Ephemeral });
+  // Reject self-transfers and bots; require the target to satisfy isStaff(),
+  // which covers ROLE_ID_TO_PING + ADDITIONAL_STAFF_ROLES — the same staff
+  // definition used by every other gate in the bot. The previous check only
+  // looked at ROLE_TO_PING_ID, missing additional staff roles.
+  if (!guildMember || guildMember.user.bot || !isStaff(guildMember)) {
+    return interaction.reply({
+      content: 'The target member must have the staff role.',
+      flags: MessageFlags.Ephemeral
+    });
+  }
+  if (guildMember.id === interaction.user.id) {
+    return interaction.reply({
+      content: 'You cannot transfer the ticket to yourself.',
+      flags: MessageFlags.Ephemeral
+    });
   }
 
   // Defer before the DB write + rename so the interaction token survives.