fix: hybrid deploy without OPcache tool, tolerant of missing secrets

- No cachetool: its web adapter needs PHP below www.ep-reisen.de/typo3temp,
  which is the static docroot in the hybrid setup (blocked, and not the
  release's typo3temp). Not needed: the exporter's front controller stubs
  resolve the "current" symlink with readlink() on every request.
- additional.php only merges secrets.php when it returns an array:
  Deployer creates an empty shared file on the first deploy.
- public/.htaccess sets TYPO3_CONTEXT=Production/Staging for
  staging.ep-reisen.de, the smoke-test vhost.
- dep host:check: read-only checks of the host before the first deploy.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

config/system/additional.php

@@ -61,7 +61,9 @@ if (getenv('IS_DDEV_PROJECT') == 'true') {
     );
 }
 
-if (is_file(__DIR__ . '/secrets.php')) {
+// Deployer creates an empty secrets.php if none exists yet: only an array counts
+$secrets = is_file(__DIR__ . '/secrets.php') ? require __DIR__ . '/secrets.php' : null;
+if (is_array($secrets)) {
     $withoutEmptyValues = static function (array $values) use (&$withoutEmptyValues): array {
         foreach ($values as $key => $value) {
             if (is_array($value)) {
@@ -74,7 +76,8 @@ if (is_file(__DIR__ . '/secrets.php')) {
     };
     $GLOBALS['TYPO3_CONF_VARS'] = array_replace_recursive(
         $GLOBALS['TYPO3_CONF_VARS'],
-        $withoutEmptyValues(require __DIR__ . '/secrets.php')
+        $withoutEmptyValues($secrets)
     );
     unset($withoutEmptyValues);
 }
+unset($secrets);