refactor(engine): add inserted_at_date to v1_payload

[mrkaye97]

Description

The plan here is to prepare to re-partition v1_payload and update its PK to use inserted_at_date, so we can enforce a more genuine "unique" constraint on (external_id, inserted_at_date) (which is extremely unlikely to collide by chance.

Fixes # (issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking changes to code which doesn't change any behaviour)

Checklist

Changes have been:

• Documented (where applicable)
• Added to CHANGELOG (where applicable) -- see Keep a Changelog

---

🤖 AI Disclosure

• I acknowledge that an LLM was used in the creation of this Pull Request, in accordance with Hatchet's AI_POLICY.md.

• Details: Claude to write the if/else logic in the migration since I never remember how to do that

[vercel]

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Project	Deployment	Actions	Updated
hatchet-docs	Ready	Preview	Sep 5, 2026 5:26pm UTC

[greptile-apps]

Greptile Summary

Adds and backfills v1_payload.inserted_at_date in preparation for date-aware partitioning and uniqueness.

• Introduces a resumable, non-transactional batched backfill and then enforces NOT NULL.
• Populates the date from inserted_at for new payload writes.
• Updates the schema and generated sqlc model/read mappings for the new column.

Confidence Score: 5/5

The PR appears safe to merge with no concrete blocking or non-blocking defects identified.

The migration's rerun behavior is coherent, current writes derive the new value from inserted_at, and the generated model, SELECT order, scan destinations, and INSERT columns remain consistent.

_{Reviews (1): Last reviewed commit: "feat: wire up writes" | Re-trigger Greptile}

[github-actions]

⚠️ Optional test failure: The load-online-migrate job failed on this PR. This check is non-mandatory and does not block merging, but may be worth investigating. View logs

[github-actions]

⚠️ Optional test failure: The load-online-migrate job failed on this PR. This check is non-mandatory and does not block merging, but may be worth investigating. View logs

[github-actions]

⚠️ Optional test failure: The load-online-migrate job failed on this PR. This check is non-mandatory and does not block merging, but may be worth investigating. View logs

[github-actions]

⚠️ Optional test failure: The load-online-migrate job failed on this PR. This check is non-mandatory and does not block merging, but may be worth investigating. View logs