refactor: type ComposableOrder.creationDate as bigint and remove double-conversion (COW-1007)

[lgahdl]

Summary

• blockHandler.ts used BigInt(Number(event.block.timestamp)) — the intermediate Number() is unnecessary since event.block.timestamp is already a bigint
• ComposableOrder.creationDate was typed as number, requiring a BigInt() cast at every DB insert site; changed to bigint to match the discreteOrder.creationDate column type
• creationDate: 0 sentinel in the terminal-order path updated to 0n to match the new type

No schema changes

validTo remains t.integer() — intentional, as it is constrained to uint32 by the EVM order-UID encoding. All other epoch timestamp columns already use bigint.

Test plan

• pnpm typecheck — clean
• pnpm test — 66 tests, all pass

🤖 Generated with Claude Code

[linear-code]

COW-1007

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	tsx@​4.22.3

View full report

[lgahdl]

Review: COW-1007 — Timestamp field standardization

Code Quality: PASS — Removes a double-conversion anti-pattern (BigInt(Number(event.block.timestamp)) where the intermediate Number() is unnecessary since event.block.timestamp is already a bigint). Aligns the ComposableOrder.creationDate type with the discreteOrder.creationDate column type (bigint), eliminating the BigInt() cast that was required at every DB insert site.

Coherence: PASS — The changes are exactly scoped to what the COW-1007 audit identified. validTo correctly remains t.integer() — it is constrained to uint32 by the EVM order-UID encoding. No schema migrations needed.

Functionality: PASS — No behavior change. The same values are written to the DB. All 66 tests pass, including the orderbookClient tests which exercise the creationDate path.

[jeffersonBastos]

Superseded by #102 (final-qa → develop). Verified that this PR's changes (COW-1007) are fully contained in the consolidated final-qa branch. Closing to merge everything through the single QA branch per the agreed plan — no work is lost.