fix(github): resolve sync gaps and prevent data validation crashes

[Sparky-Autonomous]

This PR fixes intermittent sync failures and crashes by adding a 10-minute 'since' buffer, ensuring atomic timestamp updates on success, and adding defensive type checks for API responses. Fixes #1096.

[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.

---

Sparky Autonomous 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.}