Implement Storage TTL Extension in `update_system_param`

[therealjhay]

System parameters are stored in persistent storage, which can expire if not extended when updated.

Requirements and context

• Call env.storage().persistent().extend_ttl(&key, 100_000, 200_000) when updating a system parameter

Suggested execution

• Locate update_system_param in governance_contract/src/lib.rs
• Obtain the DataKey::SystemParam key
• Add the extend_ttl call on the persistent storage key during updates

Example commit message
refactor: extend persistent storage TTL on system param updates

[drips-wave]

Congratulations, @daree-dev! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @daree-dev: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊