Standardize creator timestamp formatting

[utahkanz-ops]

Summary

• Added a shared formatIsoTimestamp helper that normalizes timestamp inputs to a single UTC ISO 8601 representation with milliseconds. Creator list items and creator detail responses now use the helper for createdAt and updatedAt, so clients receive consistently formatted timestamp strings across those response paths.

Issue

• Closes Add helper for producing consistent ISO timestamp strings in responses #345

Changes

• Added src/utils/iso-timestamp.utils.ts with validation for invalid timestamp values.
• Added unit coverage confirming Date, string-with-offset, and numeric timestamp inputs all produce the same ISO 8601 UTC output.
• Included createdAt and updatedAt in the creator list projection and mapped them through the new helper in mapCreatorListItem.
• Added createdAt and updatedAt to creator detail response schema and formatted database values through the helper.
• Kept placeholder creator detail responses explicit by returning createdAt: null and updatedAt: null when no database row exists.
• Updated nearby response-shape tests and serializer documentation for the new timestamp fields.

Validation

• pnpm.cmd exec jest src/utils/iso-timestamp.utils.test.ts src/modules/creators/creator-list-item.mapper.test.ts --runInBand passed.
• pnpm.cmd lint passed.
• pnpm.cmd build was run and now only fails on generated Prisma Client exports missing from @prisma/client (Prisma, PrismaClient, StellarWallet, User). This matches the local environment issue where Prisma Client generation is unavailable/stale, not the timestamp changes.

Notes

• The supplied InsightArena fork URL does not match accesslayerorg/accesslayer-server; this work used the existing verified local checkout with origin utahkanz-ops/accesslayer-server and upstream accesslayerorg/accesslayer-server.
• pnpm-lock.yaml was not modified.

[drips-wave]

@utahkanz-ops Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits