Add helper for building paginated response objects from a cursor and result set

[Chucks1093]

Summary

Every paginated endpoint constructs its response envelope (items, next_cursor, has_more) independently. A shared helper should produce a consistent paginated response shape so all endpoints return the same structure.

Scope

• Add buildPaginatedResponse<T>(items: T[], limit: number, cursorFn: (item: T) => string): PaginatedResponse<T>
• If items.length > limit, set has_more: true, pop the extra item, and set next_cursor to the cursor of the last kept item
• If items.length <= limit, set has_more: false and next_cursor: null
• Add unit tests for: exact limit, over limit, under limit, empty result set

Acceptance Criteria

• has_more: true and cursor set when results exceed limit
• has_more: false and cursor null when results at or below limit
• Empty result set returns has_more: false, empty items, null cursor
• Extra item not included in returned items array

ETA: 12 hours

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