2045 - fix rollback tests

[Cmdv]

Description

This fixes #2045 #2050

Fixed two bugs in db-sync:

Bug 1: ChainSync client hang after genesis fallback
After re-intersecting at genesis, clientTip wasn't reset to Origin, causing the pipeline policy to think the client was ahead of the server and stop requesting blocks.
Fix: Reset clientTip to Origin when re-intersecting at genesis.

Bug 2: Missing database fallback for intersection points
When no ledger state snapshots are available after restart, getLatestPoints had no intersection points to sync from.
Fix: Query database for recent blocks when no snapshots are available.

Checklist

• Commit sequence broadly makes sense
• Commits have useful messages
• New tests are added if needed and existing tests are updated
• Any changes are noted in the changelog
• Code is formatted with fourmolu on version 0.17.0.0 (which can be run with scripts/fourmolize.sh)
• Self-reviewed the diff

Migrations

• The pr causes a breaking change of type a,b or c
• If there is a breaking change, the pr includes a database migration and/or a fix process for old values, so that upgrade is possible
• Resyncing and running the migrations provided will result in the same database semantically

If there is a breaking change, especially a big one, please add a justification here. Please elaborate
more what the migration achieves, what it cannot achieve or why a migration is not possible.