Reduce load on unreachable servers by implementing exponential backoff
during connectivity failures. Check frequency decreases based on
consecutive failure count:
0-2: every cycle
3-5: ~15 min intervals
6-11: ~30 min intervals
12+: ~60 min intervals
Uses server ID hash to distribute checks across cycles and prevent
thundering herd.
ServerCheckJob and ServerConnectionCheckJob increment unreachable_count
on failures. ServerManagerJob applies backoff logic before dispatching
checks. Includes comprehensive test coverage.
