Migrate codebase from CommonJS to ES Modules

- Convert all require()/module.exports to import/export across 260+ files
- Add "type": "module" to package.json to enable ESM by default
- Add migrations/package.json with "type": "commonjs" to keep db-migrate compatible
- Convert eslint.config.js to ESM with sourceType: "module"
- Replace __dirname/__filename with import.meta.dirname/import.meta.filename
- Replace require.main === module with process.argv[1] === import.meta.filename
- Remove 'use strict' directives (implicit in ESM)
- Convert dynamic require() in switch statements to static import lookup maps
  (dns.js, domains.js, backupformats.js, backupsites.js, network.js)
- Extract self-referencing exports.CONSTANT patterns into standalone const
  declarations (apps.js, services.js, locks.js, users.js, mail.js, etc.)
- Lazify SERVICES object in services.js to avoid circular dependency TDZ issues
- Add clearMailQueue() to mailer.js for ESM-safe queue clearing in tests
- Add _setMockApp() to ldapserver.js for ESM-safe test mocking
- Add _setMockResolve() wrapper to dig.js for ESM-safe DNS mocking in tests
- Convert backupupload.js to use dynamic imports so --check exits before
  loading the module graph (which requires BOX_ENV)
- Update check-install to use ESM import for infra_version.js
- Convert scripts/ (hotfix, release, remote_hotfix.js, find-unused-translations)
- All 1315 tests passing

Migration stats (AI-assisted using Cursor with Claude):
- Wall clock time: ~3-4 hours
- Assistant completions: ~80-100
- Estimated token usage: ~1-2M tokens

Co-authored-by: Cursor <cursoragent@cursor.com>

src/directoryserver.js

@@ -1,6 +1,25 @@
-'use strict';
+import assert from 'node:assert';
+import AuditSource from './auditsource.js';
+import BoxError from './boxerror.js';
+import constants from './constants.js';
+import debugModule from 'debug';
+import eventlog from './eventlog.js';
+import * as ipaddr from './ipaddr.js';
+import * as groups from './groups.js';
+import ldap from 'ldapjs';
+import path from 'node:path';
+import paths from './paths.js';
+import * as reverseProxy from './reverseproxy.js';
+import safe from 'safetydance';
+import * as settings from './settings.js';
+import shellModule from './shell.js';
+import * as users from './users.js';
+import util from 'node:util';
 
-exports = module.exports = {
+const debug = debugModule('box:directoryserver');
+const shell = shellModule('directoryserver');
+
+export {
     getConfig,
     setConfig,
 
@@ -10,29 +29,11 @@ exports = module.exports = {
     checkCertificate,
 };
 
-const assert = require('node:assert'),
-    AuditSource = require('./auditsource.js'),
-    BoxError = require('./boxerror.js'),
-    constants = require('./constants.js'),
-    debug = require('debug')('box:directoryserver'),
-    eventlog = require('./eventlog.js'),
-    ipaddr = require('./ipaddr.js'),
-    groups = require('./groups.js'),
-    ldap = require('ldapjs'),
-    path = require('node:path'),
-    paths = require('./paths.js'),
-    reverseProxy = require('./reverseproxy.js'),
-    safe = require('safetydance'),
-    settings = require('./settings.js'),
-    shell = require('./shell.js')('directoryserver'),
-    users = require('./users.js'),
-    util = require('node:util');
-
 let gServer = null, gCertificate = null;
 
 const NOOP = function () {};
 
-const SET_LDAP_ALLOWLIST_CMD = path.join(__dirname, 'scripts/setldapallowlist.sh');
+const SET_LDAP_ALLOWLIST_CMD = path.join(import.meta.dirname, 'scripts/setldapallowlist.sh');
 
 async function getConfig() {
     const value = await settings.get(settings.DIRECTORY_SERVER_KEY);