"""Normalize a base URL by ensuring it has a protocol and a trailing slash.

This function processes a given URL to ensure it is in a standardized format. It adds
'http://' or 'https://' if no protocol is specified, with 'http://' being used for
local IP addresses or 'localhost'. It also ensures the URL ends with a trailing slash.

Args:
    url (str): The URL to normalize. If empty, it is returned as is.

Returns:
    str: The normalized URL with a protocol and trailing slash.

Examples:
    >>> normalize_base_url('example.com')
    'https://example.com/'
    >>> normalize_base_url('http://example.com')
    'http://example.com/'
    >>> normalize_base_url('localhost')
    'http://localhost/'
    >>> normalize_base_url('192.168.1.1')
    'http://192.168.1.1/'
"""
You should write code starting with:
def normalize_base_url(url: str) -> str:
    pass

