feat: ChatGPT Custom GPT support in chat bot + sqcp SMTP routing fix

- chat.ts: system prompt now includes step-by-step ChatGPT Custom GPT
  setup (openapi.json import + OAuth), Claude/Cursor/Windsurf config,
  and mortgage broker guidance — bot no longer incorrectly says ChatGPT
  is unsupported
- smtp.ts: all sqcp_* accounts now route to mail.squaremcp.com (SQCP_SMTP_HOST)
  instead of the fetcherpay server
- tools.ts: ACCOUNT_PARAM description now lists all 14 mailboxes including
  the 7 squaremcp.com accounts so Claude picks the right one without guessing
- package.json: postinstall hook runs imapflow patch script after npm install
- hermes-k8s.yaml: updated image digest to current production build

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/tools.ts

@@ -20,7 +20,7 @@ const ACCOUNT_PARAM = {
   account: {
     type: 'string',
     enum: ['yahoo', 'fetcherpay', 'garfield', 'sales', 'leads', 'founder', 'gmail', 'sqcp_garfield', 'sqcp_info', 'sqcp_sales', 'sqcp_support', 'sqcp_founder', 'sqcp_contact', 'sqcp_admin'],
-    description: 'Which mailbox to use: "yahoo" (gheron01@yahoo.com), "fetcherpay" (garfield.heron@fetcherpay.com), "garfield" (garfield@fetcherpay.com), "sales" (sales@fetcherpay.com), "leads" (leads@fetcherpay.com), "founder" (founder@fetcherpay.com), or "gmail" (Gmail account). Defaults to "yahoo".',
+    description: 'Which mailbox to use: "yahoo" (gheron01@yahoo.com), "fetcherpay" (garfield.heron@fetcherpay.com), "garfield" (garfield@fetcherpay.com), "sales" (sales@fetcherpay.com), "leads" (leads@fetcherpay.com), "founder" (founder@fetcherpay.com), "gmail" (garfield.heron@gmail.com), "sqcp_garfield" (garfield@squaremcp.com), "sqcp_info" (info@squaremcp.com), "sqcp_sales" (sales@squaremcp.com), "sqcp_support" (support@squaremcp.com), "sqcp_founder" (founder@squaremcp.com), "sqcp_contact" (contact@squaremcp.com), "sqcp_admin" (admin@squaremcp.com). Defaults to "yahoo".',
   },
 };