import unicodedata


def normalize_search_text(value: str | None) -> str:
    if not value:
        return ""

    value = (
        value.casefold()
        .replace("ä", "ae")
        .replace("ö", "oe")
        .replace("ü", "ue")
        .replace("ß", "ss")
    )
    normalized = unicodedata.normalize("NFKD", value)
    return "".join(char for char in normalized if not unicodedata.combining(char))