refactor(api): simplify response types from tuple to direct Zod inference

[navin-moorthy]

Summary

API response types use a non-standard tuple pattern [T, ...T[]] to enforce non-empty arrays at the type level, but Zod already validates this at runtime with .nonempty(). This adds unnecessary type complexity.

Current Pattern

export type CreateCategoryResponse = [
  z.infer<typeof CreateCategoryResponseSchema>[number],
  ...z.infer<typeof CreateCategoryResponseSchema>,
];

Proposed Change

export type CreateCategoryResponse = z.infer<typeof CreateCategoryResponseSchema>;
// Trust Zod .nonempty() validation at runtime

Affected Files

• src/app/api/category/create-user-category/route.ts
• src/app/api/category/update-user-category/route.ts
• src/app/api/tags/add-tag-to-bookmark/route.ts
• src/app/api/tags/remove-tag-from-bookmark/route.ts

Notes

Breaking Change: API response type changes affect mobile app consumers. Coordinate with mobile team before implementing.

Priority

P3 - Nice to have, low effort (30 min)

[linear]

REC-96