Reject booleans in from_timestamp_ms, consistent with from_timestamp

[bysiber]

Summary

from_timestamp_ms doesn't reject boolean values, unlike from_timestamp. This allows DateTime(format="timestamp_ms") to silently accept True/False as valid timestamps.

Problem

from_timestamp has an explicit boolean guard:

def from_timestamp(value):
    if value is True or value is False:
        raise ValueError("Not a valid POSIX timestamp")
    value = float(value)
    ...

But from_timestamp_ms converts to float first:

def from_timestamp_ms(value):
    value = float(value)          # float(True) = 1.0, float(False) = 0.0
    return from_timestamp(value / 1000)  # boolean check sees 0.001, not True

Since float(True) produces 1.0, by the time from_timestamp is called, the value is already a float and the value is True identity check fails. This means:

• DateTime(format="timestamp") correctly rejects True/False
• DateTime(format="timestamp_ms") silently accepts them, deserializing True as a datetime

Fix

Add the same boolean rejection to from_timestamp_ms before the float() conversion.