[beekld]

Summary

The FDv2 synchronizer loop measured its deadlines against the wall clock. When the system clock stepped backwards, every pending deadline was delayed by the size of the step. If every synchronizer was parked for 5 minutes and the clock stepped back an hour, no synchronizer ran for 65 minutes.

These deadlines now use MonotonicTime, a small value class over System.nanoTime(), so changes to the system clock don't move them.

Stacked on #252.

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Note

Overview
FDv2 synchronizer orchestration previously scheduled recovery, fallback, park/unpark, and FDv1 fallback TTL deadlines using wall-clock Instant. A backward system clock step could postpone those deadlines and keep sources parked or on FDv1 longer than intended.

This PR introduces MonotonicTime (backed by System.nanoTime()) and wires it through FDv2DataSource, SourceManager, and SynchronizerFactoryWithState for all internal wait/deadline logic (awaitUntil, earliest, parking, fallback end times). MonotonicTimeTest covers comparison and duration math across nanosecond counter overflow.

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