added Username or password do not match" + lockout warning

server/routes.js

   if (existing && existing.active === 0) return json(res, 403, { error: 'This account has been deactivated' });
 
   let u = (existing && A.verifyPassword(password, existing.pw_salt, existing.pw_hash)) ? existing : null;
+  let bzMsg = null;
   if (!u) {
     const bz = await BZ.validateLogin(email, password);
     if (bz.ok) u = provisionFromBizgaze(email, bz);
     else if (bz.error) return json(res, 503, { error: bz.error });
+    else bzMsg = bz.message || null; // BizGaze was configured and rejected the credentials
+  }
+  if (!u) {
+    // Specific feedback where we can be truthful:
+    if (existing) return json(res, 401, { error: 'Incorrect password. Please try again.' });
+    // No local account. BizGaze (the identity provider) doesn't reveal whether an email
+    // exists, so when it rejects we surface its own message (covers wrong password +
+    // any lockout warning). Only when BizGaze isn't in play can we say "not registered".
+    if (bzMsg) return json(res, 401, { error: bzMsg });
+    return json(res, 404, { error: 'This email is not registered.' });
   }
-  if (!u) return json(res, 401, { error: 'invalid credentials' });
 
   const tok = A.token();
   const ttl = remember ? 1000 * 60 * 60 * 24 * 30 : SESSION_TTL; // 30 days if remembered, else 24h