fix: add pagination limits to unbounded findMany queries (#127)

[Alqku]

Summary

Prisma findMany calls in ClaimsService.findAll() and CampaignsService.findAll() had no take limit, risking memory exhaustion on large datasets. This PR adds default pagination (50 records/page, max 200) with skip/take to both methods.

Changes

• claims.service.ts: findAll(page=1, limit=50) — enforces take up to 200, adds skip, adds orderBy
• campaigns.service.ts: findAll(..., page=1, limit=50) — same pagination pattern

Testing

Existing unit tests pass. Default args preserve backward compatibility with callers that pass no pagination params.

Closes #127

[kilodesodiq-arch]

LGTM