fix(i18n): update SearchBar placeholder for translation support

- Change SearchBar placeholder text to utilize translation function for improved internationalization.
- Ensure consistency in language context across the application by integrating translation keys.

src/components/header/SearchBar.js

@@ -244,7 +244,7 @@ const SearchBar = () => {
     >
       <TextField
         ref={inputRef}
-        placeholder="Produkte suchen..."
+        placeholder={t('search.searchProducts')}
         variant="outlined"
         size="small"
         fullWidth