feat: implement creator list sort defaults

[wheval]

Summary

• Added src/constants/creator-list-sort.constants.ts to centralize default creator list sort field/order.
• Updated src/modules/creator/creator.utils.ts to use shared defaults instead of inline fallback literals.
• Updated src/modules/creators/creators.schemas.ts to use the same shared defaults in Zod query defaults.
• Kept constants module lightweight and logic-free, with sort mapping/validation behavior unchanged.

Closes #39

Testing

Closes #39

• pnpm lint
• pnpm build
• pnpm exec prisma generate when schema or generated types changed

Checklist

• Linked issue or backlog item
• No secrets or live credentials added
• Docs updated if setup or env changed
• Change is scoped to one problem

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