Handle integer-valued float multipleOf divisors exactly

[ShipItAndPray]

Summary

• treat integer-valued float multipleOf divisors with exact integer modulo logic
• keep the existing float fast path and Fraction fallback for non-integer float divisors
• add regression coverage for large integers across validator drafts

Reproduction

from jsonschema import validate

validate(9007199254740995, {"type": "integer", "multipleOf": 11})
validate(9007199254740995, {"type": "integer", "multipleOf": 11.0})

Before this change, the second validation incorrectly failed.

Closes #1159

Testing

• uv run python -m unittest jsonschema.tests.test_validators.TestDraft3Validator.test_large_integer_multiple_of_integer_valued_float jsonschema.tests.test_validators.TestDraft4Validator.test_large_integer_multiple_of_integer_valued_float jsonschema.tests.test_validators.TestDraft6Validator.test_large_integer_multiple_of_integer_valued_float jsonschema.tests.test_validators.TestDraft7Validator.test_large_integer_multiple_of_integer_valued_float jsonschema.tests.test_validators.TestDraft201909Validator.test_large_integer_multiple_of_integer_valued_float jsonschema.tests.test_validators.TestDraft202012Validator.test_large_integer_multiple_of_integer_valued_float
• uv run python -m unittest jsonschema.tests.test_validators