Add standalone mode with @simpleworkjs/orm-backed user/host stores

- Add standalone.enabled config flag to switch between LDAP+SSO and
  ORM-backed backends without changing the production code path
- New ORM models: StandaloneUser (uid, passwordHash, sshPublicKeys,
  groups) and StandaloneHost (slug, displayName, kind, metadata)
- user_file.js and hosts_file.js implement the same interfaces as the
  LDAP client and accessibleHosts() respectively
- models/user_ldap.js and utils/access.js become conditional facades
  that delegate based on conf.standalone.enabled at require time
- Zero changes to ssh_server.js core logic, bridge.js, key_inject.js,
  tui_picker.js, or any other consumer
- Fix ssh_server.js: use ?? instead of || for listenPort (0 is falsy)
- Fix ssh_server.js: register session listeners before awaiting
  audit.create() so client exec/shell requests aren't rejected
- Patch StringField.toSequelize() and IntegerField.toSequelize() to
  pass through primaryKey (the ORM's UUIDField already does this)
- 47 tests pass (24 existing + 15 new unit + 3 existing integration
  + 5 new standalone integration)
- Defaults to SQLite; any Sequelize dialect works via conf.orm

Co-Authored-By: Claude <noreply@anthropic.com>

nodejs/conf/base.js

@@ -98,6 +98,21 @@ module.exports = {
 		maxEvents: 50000,
 	},
 
+	// Standalone mode: run without LDAP or SSO Manager. When enabled, user
+	// authentication and host discovery use @simpleworkjs/orm-backed stores
+	// (Sequelize, defaulting to SQLite) instead of the directory services.
+	standalone: {
+		enabled: false,
+	},
+
+	// ORM config for standalone mode. Passed through to Sequelize — any dialect
+	// works. Defaults to SQLite for zero-dependency local dev.
+	orm: {
+		dialect: 'sqlite',
+		storage: './data/standalone.sqlite',
+		logging: false,
+	},
+
 	// Orchestrator-only keys (ignored by the app, read by theta-env).
 	stack: {},
 };