Fix Psalm MixedArgument in initial state product name wiring

[Copilot]

static-psalm-analysis dev-stable30 failed on BeforeTemplateRenderedListener because provideInitialState() received a mixed value from IConfig::getSystemValue(). This change removes the mixed-type path by using the string-typed config accessor for productName.

• Root cause

  • IInitialState::provideInitialState('productName', ...) was fed by getSystemValue('ionos_product_name', ''), which Psalm infers as mixed.

• Change

  • Switched productName config read to getSystemValueString('ionos_product_name') in lib/Listener/BeforeTemplateRenderedListener.php.
  • No behavior change intended; only type certainty at the call site.

• Code snippet

  $this->initialState->provideInitialState(
      'productName',
      $this->config->getSystemValueString('ionos_product_name')
  );