[BUG] Events with identical created_at timestamps returned in non-deterministic order violating NIP-01

[saniddhyaDubey]

Describe the bug
findByFilters in event-repository.ts orders query results by event_created_at DESC only. When multiple events share the same created_at timestamp, the secondary sort by event_id ASC required by NIP-01 is missing, resulting in non-deterministic ordering of tied events across different clients and relays.

Three concrete scenarios where this manifests:

1. High frequency publishing - a client publishes multiple events within the same second, two subscribers receive them in different orders from the same relay.
2. limit: 1 with timestamp collision - two events from the same pubkey have identical created_at, different clients get different "latest" events unpredictably.
3. Cross-relay inconsistency - same REQ sent to nostream and a NIP-01 compliant relay returns events in different orders, causing inconsistent feeds for the same subscription.

To Reproduce
Steps to reproduce the behavior:

1. Publish two or more events with identical created_at timestamps to the relay
2. Send a REQ message with a limit filter: ["REQ", "sub1", { "limit": n }]
3. Observe that the order of events with the same created_at is non-deterministic and inconsistent across different clients or relays

Expected behavior
Per NIP-01, when two or more events share the same created_at timestamp, they must be returned ordered by event_id ASC (lexicographical order) as a tiebreaker. The same REQ with the same filters should return events in the same deterministic order across all clients and relays.

System:

• OS: N/A — code-level bug, not system specific
• Platform: docker, standalone
• Version: v2.1.0

Logs
N/A — bug produces no error logs, only incorrect event ordering in query results.