fix: handle invalid character error in Generate HOTP (issue #2445)

[vanhci]

Summary\n\nWhen Generate HOTP receives invalid characters in the input, it throws a raw TypeError instead of showing a user-friendly error message.\n\n## Fix\n\nWrapped the operation logic in a try-catch block to catch TypeError and display a clear message: "Invalid character found: X".\n\n## Testing\n\n- [ ] Test with invalid characters (|,;,\ etc.) shows clear error message\n- [ ] Test with valid input still works correctly

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

vanhci seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[HackingRepo]

also @vanhci, the summary must be clear and readable