Guard transaction replay height overflow

[giwaov]

Summary

• Saturate the maximum accepted replay height when the current height is near max uint64.
• Prevent unsigned wraparound from rejecting otherwise valid transaction heights.
• Add a regression case for near-max replay height bounds.

Why

CheckReplay calculated height + BlockAcceptanceRange directly. Near max uint64, that addition can wrap to a small value and make a same-height transaction fail the upper-bound check.

Testing

• git diff --check
• Not run: Go toolchain is not installed in this environment.