Email ticketing fixes, comms polish, and .env cleanup

Inbound:
- Gmail poll query is:unread in:inbox (was category:primary, which matched
  nothing on a no-tabs Workspace inbox)

Outbound email:
- Closed/escalation auto-emails editable via TICKET_CLOSE_MESSAGE and new
  TICKET_ESCALATION_EMAIL_MESSAGE; drop the staff signature from closing emails
- Replies quote the customer's latest message (gmail_quote markup so clients
  collapse it), embed custom emoji inline via CID attachment, and strip Discord
  role mentions
- Tagline spacing fix in the company signature

Discord side:
- Suppress all mentions in log + transcript posts (no more pinging on close)
- Drop the staff-role ping from new-ticket and follow-up notifications
- Ticket channels inherit category permissions instead of setting per-channel
  overwrites (removes the Manage Roles requirement)

Gmail folders:
- Folder/label routing (gmailLabels.js) with /folder; close files to Complete

Config:
- Remove ~56 stale .env keys for long-removed features; refresh stale copy

Docs:
- Design specs for folder routing, email-flow toggle, and per-staff metrics

services/debugLog.js

@@ -36,7 +36,7 @@ async function sendToChannel(channelId, embed, overrideClient) {
   if (!c || !channelId) return;
   try {
     const channel = await c.channels.fetch(channelId);
-    if (channel) await channel.send({ embeds: [embed] });
+    if (channel) await channel.send({ embeds: [embed], allowedMentions: { parse: [] } });
   } catch (_) {
     // ignore send failures
   }
@@ -59,7 +59,8 @@ async function logError(context, error, interaction = null, overrideClient = nul
     const message = redactPII(error.message || String(error));
     const stack = redactPII(error.stack || error.message || String(error)).slice(0, 1500);
     await channel.send({
-      content: `\`[${context}]\` ${message}\n${userLine}${commandLine}\n\`\`\`${stack}\`\`\``
+      content: `\`[${context}]\` ${message}\n${userLine}${commandLine}\n\`\`\`${stack}\`\`\``,
+      allowedMentions: { parse: [] }
     });
   } catch (_) {
     // ignore send failures