simplify: rename CONFIG channels, dedup hasStaffRole, drop enforceEmbedLimit

- Rename CONFIG.TRANSCRIPT_CHAN -> CONFIG.TRANSCRIPT_CHANNEL_ID and
  CONFIG.LOG_CHAN -> CONFIG.LOGGING_CHANNEL_ID across 9 callsites so
  CONFIG keys match their .env names — no more "grep .env, find nothing"
  for new readers
- Replace handlers/commands.js#hasStaffRole with utils.js#isStaff
  (was a verbatim copy)
- Delete utils.js#enforceEmbedLimit and its 2 callsites; both inputs are
  bounded well under the 6000-char Discord embed cap, so the trim was
  defensive code that never fired

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/debugLog.js

@@ -69,7 +69,7 @@ async function logTicketEvent(action, fields, interaction = null) {
   if (interaction?.user?.tag) {
     embed.setFooter({ text: interaction.user.tag });
   }
-  await sendToChannel(CONFIG.LOG_CHAN, embed, interaction?.client);
+  await sendToChannel(CONFIG.LOGGING_CHANNEL_ID, embed, interaction?.client);
 }
 
 module.exports = {