fix: raise Dovecot IMAP login capacity

AI-Co-Authored-By: Codex

docker/dovecot/mailhub.conf

@@ -56,7 +56,7 @@ namespace inbox {
 service imap-login {
   chroot =
   process_min_avail = 1
-  process_limit = 24
+  process_limit = 64
 
   inet_listener imaps {
     ssl = yes

test/dovecot-config.test.js

@@ -57,7 +57,7 @@ test('Dovecot and app defaults stay modest on low-resource mail hosts', () => {
   assert.match(appService, /UV_THREADPOOL_SIZE: \$\{UV_THREADPOOL_SIZE:-2\}/);
   assert.match(envExample, /^UV_THREADPOOL_SIZE=2$/m);
   assert.match(mailConfig, /service imap-login \{[\s\S]*process_min_avail = 1/);
-  assert.match(mailConfig, /service imap-login \{[\s\S]*process_limit = 24/);
+  assert.match(mailConfig, /service imap-login \{[\s\S]*process_limit = 64/);
   assert.match(mailConfig, /service pop3-login \{[\s\S]*process_min_avail = 0/);
   assert.match(mailConfig, /service pop3-login \{[\s\S]*process_limit = 8/);
 });