fix: make bond early_unlock_admin nullable

[rafa-stacks]

Description

The setup-bond pox-5 event no longer carries an early_unlock_admin field, but the bonds table still defined the early_unlock_admin column as NOT NULL, forcing ingestion to write an empty-string placeholder. This makes the column nullable so bond creation can simply skip it.

1. Motivation for change: keep the schema in sync with the updated setup-bond event and stop persisting a meaningless placeholder value.
2. What was changed:
   • bonds migration: early_unlock_admin is now nullable (dropped NOT NULL).
   • Ingestion (updateBond): no longer sets early_unlock_admin (removed the '' placeholder + its TODO); the column defaults to NULL.
   • DbBondInsertValues: dropped the early_unlock_admin field (no longer written).
   • DbBond: early_unlock_admin read type is now string | null.
3. How does this impact application developers: no API-visible change — early_unlock_admin is not exposed in any response/serializer; it remains an internal column (now nullable).
4. Link to relevant issues and documentation: follow-up to the pox-5 setup-bond event change (feat: capture bond registration BTC/sBTC lockup data #2579).

Type of Change

• New feature
• Bug fix
• API reference/documentation update
• Other

Does this introduce a breaking change?

No. Targets the unreleased pox5 line; the column is internal and not serialized in any API response.

Are documentation updates required?

• Link to documentation updates:

Testing information

1. Testing is covered by the existing simulated tests/api/pox5/bonds.test.ts suite — the SETUP_BOND_DATA fixture no longer includes early_unlock_admin, matching the new event shape.
2. Not a reproduction-style bug.
3. Affected code paths: pox-5 setup-bond ingestion (pg-write-store → updateBond), bonds migration, and the bond DB types.
4. No other affected projects.
5. Watch out for: nothing reads early_unlock_admin on the read path; BOND_COLUMNS still selects it (now returns null). Verified with npm run test:api:pox5 (bonds suite: 17/17 passing).

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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