Add cursor pagination to the notifications list endpoint

[mikewheeleer]

Paginate notifications

Description

notifications list returns everything at once. This issue adds cursor pagination.

Requirements and context

• Repository scope: Agentpay-Org/Agentpay-backend only.
• Add opaque-cursor pagination to the notifications list endpoint with a bounded page size.
• Return a stable nextCursor; reject invalid cursors.
• Cover first page, next page, end, and invalid cursor in tests.

Suggested execution

• Fork the repo and create a branch
• git checkout -b feature/notifications-92-cursor
• Implement changes
  • Write code in: the relevant module.
  • Write comprehensive tests in: cover the new behaviour and edge cases.
• Test and commit

Test and commit

• Run npm run lint, npm test, and npm run build.
• Cover edge cases: first page, next, end, invalid cursor.
• Include the full test output in the PR description.

Example commit message

feat(notifications): add cursor pagination

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the AgentPay community on Discord: https://discord.gg/eXvRKkgcv
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — a 5-star rating is much appreciated.