Improve test time is synced

[jakubno]

• date %s is truncating the time to seconds -> it could happen that there was 0.999 and in local 1.001 and the test failed
• Increase the wait time and make the test little bit more relaxed

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Note

Increase delay, use millisecond-precision date, and widen tolerance to reduce flaky time sync failures.

• Tests (tests/periodic-test/time-is-synchronized/index.ts):
  • Increase sleep from 5s to 15s to create a clearer time delta.
  • Use millisecond-precision timestamp (date +%s%3N) and parse as float, then divide by 1000.
  • Relax comparison threshold from 1s to 2s.

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