Implement on-chain reputation scoring for payers and creators

[Kingsman-99]

Overview

Build a reputation system that tracks on-chain behaviour for addresses. Payers earn points for paying on time; creators earn points for invoices that successfully release. Reputation scores can be queried and used as optional gate conditions on future invoices.

Requirements

• rep_key(address) storage key (persistent) storing RepScore { paid_on_time: u32, late_pays: u32, invoices_released: u32, invoices_refunded: u32 }
• Update rep scores automatically on release (creator + payers) and refund (creator penalty)
• get_rep(env, address) -> RepScore read function
• Extend InvoiceOptions with optional min_payer_rep: Option<u32> — reject pay calls from addresses below threshold
• Emit RepUpdated { address, score } event after each update
• Write tests covering all rep update paths and the min_rep gate

Acceptance Criteria

• Rep scores update correctly on release and refund
• min_payer_rep gate rejects low-rep payers
• get_rep returns correct accumulated scores
• Storage snapshot updated for rep_key
• All existing tests pass
• cargo test --workspace passes with zero failures
• cargo clippy --all-targets -- -D warnings produces zero warnings

Definition of Done

All CI checks must pass before the PR is reviewed.

[nurudeenheroic]

I'd be happy to contribute and deliver a reliable solution.

[Promise278]

I have experience with system design I would love to work on these please