fix(mail): restore upstream IMAP config constants zpush dropped

The replacement imap.config.php omitted constants the backend
references unconditionally — SYSTEM_MIME_TYPES_MAPPING 500'd every
authenticated request (backend construction, before login, so the
unauthenticated 401 smoke tests never hit it). Define all remaining
upstream constants with their defaults so the replacement file can
never be narrower than the template it replaces.

services/zpush/config/imap.config.php

@@ -46,3 +46,31 @@ $imap_smtp_params = array(
     'verify_peer_name' => false,
     'allow_self_signed' => true,
 );
+
+// ── Upstream defaults below — DO NOT prune. ─────────────────────────────
+// This file REPLACES the upstream template, and the backend references
+// several of these unconditionally (a missing SYSTEM_MIME_TYPES_MAPPING
+// 500'd every authenticated request on first deploy). Unused features
+// (SQL/LDAP From lookup) still need their constants defined.
+define('MAIL_MIMEPART_CRLF', "\r\n");
+define('SYSTEM_MIME_TYPES_MAPPING', '/etc/mime.types');
+define('IMAP_MEETING_USE_CALDAV', false);
+define('IMAP_SEARCH_CHARSET', 'UTF-8');
+define('IMAP_FROM_SQL_DSN', '');
+define('IMAP_FROM_SQL_USER', '');
+define('IMAP_FROM_SQL_PASSWORD', '');
+define('IMAP_FROM_SQL_OPTIONS', serialize(array(PDO::ATTR_PERSISTENT => true)));
+define('IMAP_FROM_SQL_QUERY', "select first_name, last_name, mail_address from users where mail_address = '#username@#domain'");
+define('IMAP_FROM_SQL_FIELDS', serialize(array('first_name', 'last_name', 'mail_address')));
+define('IMAP_FROM_SQL_EMAIL', '#mail_address');
+define('IMAP_FROM_SQL_FROM', '#first_name #last_name <#mail_address>');
+define('IMAP_FROM_SQL_FULLNAME', '#first_name #last_name');
+define('IMAP_FROM_LDAP_SERVER_URI', 'ldap://127.0.0.1:389/');
+define('IMAP_FROM_LDAP_USER', '');
+define('IMAP_FROM_LDAP_PASSWORD', '');
+define('IMAP_FROM_LDAP_BASE', '');
+define('IMAP_FROM_LDAP_QUERY', '(mail=#username@#domain)');
+define('IMAP_FROM_LDAP_FIELDS', serialize(array('givenname', 'sn', 'mail')));
+define('IMAP_FROM_LDAP_EMAIL', '#mail');
+define('IMAP_FROM_LDAP_FROM', '#givenname #sn <#mail>');
+define('IMAP_FROM_LDAP_FULLNAME', '#givenname #sn');