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/scripts/backupupload.js

@@ -1,16 +1,18 @@
 #!/usr/bin/env node
 
-'use strict';
-
+// --check is used by run-tests to verify sudo access works.
+// It must exit before loading the full module graph (which requires BOX_ENV).
 if (process.argv[2] === '--check') {
     console.log('OK');
     process.exit(0);
 }
 
-const backuptask = require('../backuptask.js'),
-    database = require('../database.js'),
-    debug = require('debug')('box:backupupload'),
-    safe = require('safetydance');
+const backuptask = await import('../backuptask.js');
+const database = await import('../database.js');
+const { default: debugModule } = await import('debug');
+const { default: safe } = await import('safetydance');
+
+const debug = debugModule('box:backupupload');
 
 // Main process starts here
 const remotePath = process.argv[2];
@@ -41,13 +43,11 @@ function throttledProgressCallback(msecs) {
     };
 }
 
-(async function main() {
-    await database.initialize();
+await database.initialize();
 
-    const [uploadError, result] = await safe(backuptask.upload(remotePath, format, dataLayoutString, throttledProgressCallback(5000)));
-    debug('upload completed. error: %o', uploadError);
+const [uploadError, result] = await safe(backuptask.upload(remotePath, format, dataLayoutString, throttledProgressCallback(5000)));
+debug('upload completed. error: %o', uploadError);
 
-    process.send({ result, errorMessage: uploadError?.message });
+process.send({ result, errorMessage: uploadError?.message });
 
-    process.exit(uploadError ? 50 : 0);
-})();
+process.exit(uploadError ? 50 : 0);