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/logs.js

@@ -1,15 +1,15 @@
-'use strict';
+import assert from 'node:assert';
+import child_process from 'node:child_process';
+import debugModule from 'debug';
+import path from 'node:path';
+import stream from 'node:stream';
+import { StringDecoder } from 'node:string_decoder';
 
-const assert = require('node:assert'),
-    child_process = require('node:child_process'),
-    debug = require('debug')('box:logs'),
-    path = require('node:path'),
-    stream = require('node:stream'),
-    { StringDecoder } = require('node:string_decoder'),
-    TransformStream = stream.Transform;
+const debug = debugModule('box:logs');
+const TransformStream = stream.Transform;
 
-const LOGTAIL_CMD = path.join(__dirname, 'scripts/logtail.sh');
-const KILL_CHILD_CMD = path.join(__dirname, 'scripts/kill-child.sh');
+const LOGTAIL_CMD = path.join(import.meta.dirname, 'scripts/logtail.sh');
+const KILL_CHILD_CMD = path.join(import.meta.dirname, 'scripts/kill-child.sh');
 
 class LogStream extends TransformStream {
     constructor(options) {
@@ -99,7 +99,7 @@ function journalctl(unit, options) {
     return cp;
 }
 
-exports = module.exports = {
+export {
     tail,
     journalctl,
     LogStream