feat(contracts): reputation decay, pausable escrow, cross-contract validation, and shipment events

[limxiy]

Summary

Four new contracts added to contracts/package/. No existing contract files modified.

Changes

• reputation-decay: time-decay weighted scoring — recent ratings (100%), 365–730 days (70%), 730d+ (40%); configurable thresholds at init
• escrow-pausable: admin pause/unpause halts fund_escrow and open_dispute; release_funds and refund remain unblocked; emits ContractPaused event with actor and timestamp
• cross-contract-validator: validate_and_release atomically checks shipment is DELIVERED and escrow is FUNDED before triggering release; returns structured ReleaseResult::Blocked(reason) on failure
• shipment-events: emits structured Soroban events on all 7 state transitions (ShipmentCreated, ShipmentAccepted, InTransit, Delivered, Completed, Disputed, Cancelled); topic is (event_name, shipment_id) for indexer filtering

Testing

cargo test -p reputation-decay
cargo test -p escrow-pausable
cargo test -p cross-contract-validator
cargo test -p shipment-events

Closes #921
Closes #922
Closes #923
Closes #924

[vercel]

@limxiy is attempting to deploy a commit to the Mftee's projects Team on Vercel.

A member of the Team first needs to authorize it.

[drips-wave]

@limxiy Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits