fix: insert last msg id in correct format

[zone117x]

The last_msg_id expects an integer, but it was trying to insert the msg id format received from redis e.g. <msgId>-0.

[github-actions]

Vercel deployment URL: https://signer-metrics-czkznqexl-hirosystems.vercel.app 🚀

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/pg/ingestion/pg-write-store.ts	0.00%	2 Missing ⚠️

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[CharlieC3]

Commenting here what I said in a DM:

once the signer metrics api catches up to its recorded block_height, it then starts writing to the last_redis_msg_id correctly. So if it’s just syncing blocks it already has in its DB, then the last_redis_msg_id does not update. That feels more like missing logic rather than a DB write error :thinking_face:

Are you sure this PR addresses the bug affecting the scenario described above?