4 enhance otp codes

[nehemiah-nf]

Closes #4

[thirstyape]

@nehemiah-nf please make changes as per the following comments by Copilot.

• XML documentation for properties changed to public
• Explanation here as to why the digits filter was reduced from 24 to 10
• Update CurrentIteration logic to throw an exception when TimeInterval is less than or equal to 0 (and denote the exception in XML commenting)

[nehemiah-nf]

The maximum value of binary is 0x7fffffff which is 2,147,483,647 which has only 10 digits so any modulo greater than 10 is just being redundant and not actually showing that many digits in the password. It would just be a bunch of 0s followed by the 10 digit code.

[thirstyape]

The maximum value of binary is 0x7fffffff which is 2,147,483,647 which has only 10 digits so any modulo greater than 10 is just being redundant and not actually showing that many digits in the password. It would just be a bunch of 0s followed by the 10 digit code.

Nice catch. The following should resolve, please update the OTP generation to use long internally.

var offset = hash[^1] & 0xFL;

var binary =
	((hash[offset] & 0x7FL) << 24) |
	((hash[offset + 1] & 0xFFL) << 16) |
	((hash[offset + 2] & 0xFFL) << 8) |
	(hash[offset + 3] & 0xFFL);

var password = binary % (long)Math.Pow(10, digits);

[Copilot]

Pull Request Overview

This PR enhances the OTP service by making core parameters configurable, tightening validation, and improving numeric handling in code generation.

• Secret length is now a public, settable property.
• Time interval for code validity is configurable with validation.
• Bitwise operations and digit limits updated to use long types.

Comments suppressed due to low confidence (1)

Tools/OtpService.cs:22

• The new TimeInterval setter and its validation should have unit tests covering both valid and invalid values to prevent regressions when adjusting code validity periods.

			if (value <= 0)