Reject out-of-range exp/nbf/iat NumericDate claim values

[pctablet505]

Summary

exp, nbf, and iat are validated with a plain int(payload[claim]) comparison. Python integers are arbitrary precision, so a claim like 10**50 sails through the comparison even though it can't represent a real date:

>>> import jwt
>>> tok = jwt.encode({"exp": 10**50}, "secret", algorithm="HS256")
>>> jwt.decode(tok, "secret", algorithms=["HS256"])
{'exp': 100000000000000000000000000000000000000000000000000}

RFC 7519 defines these claims as NumericDate values — seconds since the epoch representing an actual date/time. A value like this doesn't represent one, and code that reasonably converts the accepted claim with datetime.fromtimestamp() hits an uncaught OverflowError.

Fix

Add a bound matching the range datetime can represent (up to year 9999, i.e. 253402300799) and reject exp/nbf/iat values outside it with the same exception types these validators already raise for other malformed values (DecodeError for exp/nbf, InvalidIssuedAtError for iat). No behavior changes for any value in the range real tokens use.

Closes #1171.

Testing

Full suite passes locally (378 tests incl. 9 new, 0 skipped with cryptography installed): pytest tests/. ruff check, ruff format --check, and mypy jwt/api_jwt.py are clean.