feat(theme): локальный выбор и показанная тема handoff (#13)

index.php

@@ -3,6 +3,7 @@
 require_once __DIR__ . '/i18n.php';
 require_once __DIR__ . '/components/asset-url.php';
 require_once __DIR__ . '/components/site-domain.php';
+require_once __DIR__ . '/components/theme-preference.php';
 
 $configFile = __DIR__ . '/config.json';
 $config = file_exists($configFile) ? json_decode(file_get_contents($configFile), true) : [];
@@ -70,6 +71,8 @@ if (isset($config['utm']) && is_array($config['utm'])) {
 }
 
 $UTM = $get_params;
+$themeInitial = prelandThemeResolve(($UTM['theme'] ?? 'light') === 'dark' ? 'dark' : 'light');
+$themeSurface = 'preland';
 $host = $config['host'] ?? ($_SERVER['HTTP_HOST'] ?? '');
 $apiHost = $host ? (preg_match('#^https?://#', $host) ? rtrim($host, '/') : 'https://' . rtrim($host, '/')) : '';