[FEATURE] Import .jsonl file with events into the events table #406

Is your feature request related to a problem? Please describe.

Currently, there is no built-in way to seed a Nostream relay with existing data or migrate events from another relay. While operators can manually interact with the database, a standardized way to import NIP-01 compliant .jsonl files is missing. This makes relay migrations, disaster recovery, and data sharing cumbersome.

Describe the solution you'd like

I would like a CLI utility to import Nostr events from a .jsonl file into the Nostream events table.

Functional Requirements:

1. Validation: Every event must be validated before insertion (checking signature, id hash, and basic NIP-01 structure) to ensure database integrity.
2. Deduplication: The importer should gracefully handle "Duplicate Key" errors. If an event already exists in the database, it should be skipped without failing the entire batch.
3. Batch Processing: To optimize performance, events should be inserted in batches (e.g., 500–1000 events per transaction) rather than one by one.

CLI Interface Example:

# Basic import
npm run import -- ./events.jsonl

Describe alternatives you've considered

• Manual SQL Inserts: Too prone to error and fails to validate Nostr signatures.
• Using a Nostr Client to "Replay" Events: Extremely slow and puts unnecessary load on the relay's WebSocket interface and rate limiters.

Additional context

Technical Considerations:

• Backpressure & Memory: Use Node.js streams (readline interface or a custom transform stream) to process the file line-by-line. This ensures that even a 100GB file won't cause an Out-Of-Memory (OOM) error.
• Performance vs. Availability: For very large imports, the utility should ideally provide a way to throttle the import speed or run in the background to ensure the relay remains responsive to active users.
• Worker Threads: Validation (especially signature verification) is CPU-intensive. Consider using a worker pool to validate signatures in parallel before sending batches to the database.
• Ensure any rate limiting is bypassed during import operations: interact directly with the database layer (or service layer) rather than hitting the WebSocket endpoint.

Expected Outcomes:

• A new npm run import command.
• Support for .jsonl format.
• Progress Tracking: A progress bar or log showing [Processed: 50k | Inserted: 45k | Skipped: 5k | Errors: 0].
• Documentation updated in README.md.

Out of Scope:

• Broadcasting events to connected clients