Backward-compatible re-exports for HTTP Basic auth helpers.
Some callers import from tekhsi.auth.basic while internal code imports from
tekhsi.auth_basic. Keep both paths valid.
build_basic_authorization_value(username: str, password: str) -> str
Return the full value for the authorization metadata key: Basic <b64>.
parse_basic_authorization(header_value: str) -> tuple[str, str] | None
Parse Basic <b64>; return (username, password) or None if invalid.