test(disputes): add dispute-resolution refund finality coverage

[Kuhai9801]

📝 Description

Adds an end-to-end regression for the funded invoice -> dispute -> review -> resolution -> escrow refund path.

🔧 Changes Made

• Adds quicklendx-contracts/src/test_dispute_refund_flow.rs.
• Verifies post-refund alignment across invoice, dispute, escrow, accepted bid, investment, status indexes, and investor token balance.
• Verifies finality: a second refund and settlement after refund both fail with InvalidStatus and do not move funds.

🧪 Testing

• rustfmt --check --edition 2021 quicklendx-contracts/src/test_dispute_refund_flow.rs
• git diff --check
• Not run locally: cargo test / cargo clippy

🔗 Related Issues

Closes #1324

🧪 How to Test

1. cd quicklendx-contracts
2. cargo test test_dispute_refund_flow -- --nocapture

[Baskarayelu]

dispute-resolution refund finality coverage - confirms escrow and investment state land consistently after resolution. merging 👍