[PERF]: Replace offset pagination with stable cursor pagination and query budgets

[barry01-hash]

Context

Payouts, applications, users, logs, and tickets will grow continuously. Offset pagination becomes slower at depth and can skip/duplicate results when rows are inserted between requests. Flexible filters also risk expensive unbounded queries.

Scope

• Define opaque cursor contracts using a stable composite order such as (created_at, id).
• Implement forward/backward cursor pagination for collection endpoints.
• Add maximum page sizes, filter validation, and deterministic tie-breaking.
• Review query plans and add evidence-based composite indexes for common role/status/date filters.
• Avoid N+1 profile lookups and return only required fields.
• Add representative-volume performance tests and query budgets.

Acceptance criteria

• Concurrent inserts do not create duplicates or gaps while paging a fixed traversal.
• Invalid/tampered cursors return a typed 400.
• Deep-page latency stays within the documented budget on representative data.
• EXPLAIN ANALYZE evidence accompanies new indexes.
• Frontend pagination and TanStack Query cache behavior use the new contract.
• A compatibility plan exists for current offset consumers.

Relevant areas

Payout find-all, bounty find-all, support ticket listing, user queries, filters and pagination components.