Fix: Reduce snapshot frequency during initial sync

Fixes issue #1992 by making ledger state snapshot intervals configurable and significantly reducing snapshot frequency during initial sync to improve performance.

Changes:

• Added snapshot_interval configuration with following (default: 500) and lagging (default: 100,000, previously 10,000) parameters
• Fixed bug in timeToSnapshot function that was ignoring the lagging interval (previously hardcoded to False)
• When near tip, snapshots continue every 500 blocks for quick rollback recovery

New configuration:

{
 "snapshot_interval": {
   "near_tip_epoch": 580
 }
}