Settlement: cap get_all_developer_balances or paginate to bound gas for large maps

[greatest0fallt1me]

Description

CalloraSettlement::get_all_developer_balances iterates the entire developer Map and its own docs warn that >100 entries can exhaust gas. A single unbounded admin view that can hit the transaction budget is a denial-of-service vector for operators. Add pagination (offset/limit) or a hard cap so the call cannot exceed Soroban resource limits.

Requirements and Context

• Add get_developer_balances_page(caller, start, limit) with a documented max limit.
• Keep the legacy full call but reject when entry count exceeds a safe threshold, pointing operators to the paginated API and off-chain indexing.
• Document gas implications in docs/SETTLEMENT_IMPLEMENTATION.md.
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b feature/settlement-paginated-balances

2. Implement changes
   • contracts/settlement/src/lib.rs — paginated view + cap
   • docs/SETTLEMENT_IMPLEMENTATION.md — gas/pagination notes
3. Test and commit
   • cargo test -p callora-settlement
   • Test pagination boundaries and over-cap rejection
   • Include test output and notes in the PR

Example commit message

feat: add paginated developer balance query to settlement

Acceptance Criteria

• Paginated query with documented max limit
• Over-threshold full query rejected with guidance
• Pagination boundaries tested
• Gas notes documented

Guidelines

• .rs under contracts/settlement/src/, cargo test, /// docs, minimum 95% line coverage, no unwrap() in prod paths
• Clear documentation and inline comments
• Timeframe: 96 hours

[wavyboy-build]

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