Move ConfigReader and DomainResolver into XcVm\Core\Config (Composer PSR-4).
SettingsManager/SettingsRepository stay global for now (migrated together later
due to SettingsManager's large fan-out).
- Add namespace to both classes.
- Qualify still-global / ioncube refs: \XC_VM:: in ConfigReader; \CacheReader::,
\ConnectionTracker:: in DomainResolver.
- Add 'use XcVm\Core\Config\...;' to the 15 referencing files (bootstrap, CLI
commands/cron, LegacyInitializer, ModuleManager, stream + player controllers,
player views, PlaylistGenerator, ...) — call sites unchanged.
- ModuleManager::isLoadBalancer: string class_exists('ConfigReader') →
class_exists(ConfigReader::class) (the literal would now always be false).
Verified: php -l clean; PHPStan no errors; PHPUnit 295/295.