Raise ValidationError (not ValueError) for NaN in TimeDelta

[vidigoat]

Problem

A TimeDelta field raises a bare ValueError (instead of ValidationError) when it receives NaN, so loading untrusted input can crash with an exception that isn't part of marshmallow's public error contract:

from marshmallow import Schema, fields

class S(Schema):
    duration = fields.TimeDelta()

S().load({"duration": "nan"})
# ValueError: cannot convert float NaN to integer   <- leaks; expected ValidationError

"inf" / "-inf" already behave correctly (they raise ValidationError), which makes the NaN case an inconsistency rather than intended behaviour.

Cause

TimeDelta._deserialize only catches OverflowError around dt.timedelta(**kwargs):

try:
    return dt.timedelta(**kwargs)
except OverflowError as error:
    raise self.make_error("invalid") from error

float("nan") passes the earlier float(value) guard, but dt.timedelta(nan) raises ValueError — not OverflowError — so it escapes uncaught. (inf/-inf work because timedelta raises OverflowError for those.)

Fix

Catch ValueError alongside OverflowError, so NaN produces the field's standard "Not a valid period of time." error like every other invalid input:

except (OverflowError, ValueError) as error:
    raise self.make_error("invalid") from error

Extended the existing parametrized test_invalid_timedelta_field_deserialization with "nan", "inf", "-inf". Full test suite passes locally.

---

Disclosure: I used an LLM to help find and draft this fix; I've reviewed every line, reproduced the bug, and run the suite myself.

[lafrech]

Thanks.
Just a few minor comments. LLM tend to be too verbose.

[vidigoat]

Comment shortened, thanks.

On the commit message: I wasn't able to rewrite the original commit here. If you squash-merge, feel free to use just the PR title as the message.

[lafrech]

Thanks.