test(governance): add protocol config bounds matrix

[Kuhai9801]

📝 Description

Adds a focused bounds-enforcement matrix for set_fee_config and set_protocol_config.

🔧 Changes Made

• Adds quicklendx-contracts/src/test_config_bounds_matrix.rs.
• Verifies fee bps accepts 0 and 1000, rejects 1001, and preserves state after rejection.
• Verifies protocol config lower/upper boundaries for min invoice amount, max due-date days, and grace-period seconds.
• Verifies non-admin calls to both setters reject with NotAdmin and leave readable config unchanged.

🧪 Testing

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

🔗 Related Issues

Closes #1346

🧪 How to Test

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

[Baskarayelu]

a full bounds matrix on set_protocol_config / set_fee_config is exactly the guardrail coverage we wanted. merging 👍