Gmail folder auto-advance + /forward command

- Reply-cycle auto-advance: staff reply files the thread to "Awaiting Reply",
  a customer response files it to "Needs Response" (new GMAIL_LABEL_AWAITING_REPLY
  / GMAIL_LABEL_NEEDS_RESPONSE labels + autoAdvanceFolder, which only moves
  threads still in the auto-cycle and leaves hand-filed folders alone)
- /forward: forward a ticket's email to another address (handlers/commands/forward.js
  + forward composition in services/gmail.js)
- Tests for the auto-advance cycle; label fixtures updated for the new labels

handlers/messages.js

@@ -5,6 +5,7 @@ const { mongoose } = require('../db-connection');
 const { CONFIG } = require('../config');
 const { extractRawEmail, isStaff, getCleanBody } = require('../utils');
 const { getGmailClient, sendGmailReply } = require('../services/gmail');
+const { autoAdvanceFolder } = require('../services/gmailLabels');
 const { getNotifyDm } = require('../services/staffSettings');
 const { logError } = require('../services/debugLog');
 
@@ -100,6 +101,12 @@ async function handleDiscordReply(m) {
       m.author.id,
       quote
     );
+
+    // Staff just replied to the customer → advance to Awaiting Reply (unless the
+    // thread is manually filed). Fire-and-forget: a label failure must not break
+    // the reply that already went out.
+    autoAdvanceFolder(ticket.gmailThreadId, 'AWAITING_REPLY')
+      .catch(err => logError('autoAdvanceFolder(AWAITING_REPLY)', err).catch(() => {}));
   } catch (e) {
     console.error('REPLY ERROR:', e);
   }