Add anchor_settlement_count(anchor) to avoid a full list_settlements_by_anchor scan just to count

[Jagadeeshftw]

📌 Description

settlement_count_by_status(status) gives a full-history count filtered by lifecycle state without pagination, but there is no equivalent for filtering by anchor — a caller who only wants "how many settlements has this anchor ever opened" must page through list_settlements_by_anchor accumulating a Vec just to measure its length, which is both more expensive and more awkward than a direct count.

🧩 Requirements and context

• Add anchor_settlement_count(env, anchor) -> u64 scanning the full settlement history (same loop shape as settlement_count_by_status) and counting matches on anchor instead of status.
• Document the O(n) scan cost consistent with the other full-history aggregate functions.
• Add regression tests with settlements from multiple anchors interleaved.

🛠️ Suggested execution

• Add the entrypoint to src/lib.rs beside settlement_count_by_status.
• Add src/test.rs coverage for an anchor with zero, one, and many settlements, interleaved with other anchors' settlements.
• Add the new view to the README settlement table.

✅ Acceptance criteria

• anchor_settlement_count(anchor) equals the number of settlements ever opened by that anchor, regardless of status.
• It returns 0 for an anchor that has never opened a settlement.
• Existing list_settlements_by_anchor behavior is unchanged.

🔒 Security notes

A dedicated count avoids callers building an unbounded Vec client-side just to measure activity volume, keeping per-call instruction cost predictable for dashboards that poll many anchors.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours

[Jagadeeshftw]

Thanks for the interest, @Mitch5000! You currently have 6 assigned issues in this repo with no PR up yet, which is the cap (6) for this project. Please open a PR for one of them (or release it) before taking on another — issues you've already submitted a PR for don't count against this.

[Jagadeeshftw]

Assigned @Mitch5000 to this issue. Please open a PR referencing this issue (e.g. Closes #114) when you're ready. If you have questions along the way, feel free to join our contributor chat: https://t.me/+vTbe0hOUKrFhNTJl

[grantfox-oss]

🦊 GrantFox — @Mitch5000 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #114)
2. Your PR will be reviewed by the AnchorNet-Org maintainers

Good luck! Track your progress on GrantFox.

[Jagadeeshftw]

Thanks for applying here. Please also join our Telegram group here: https://t.me/+vTbe0hOUKrFhNTJl. It helps us keep communication clear while we review contributions.