Feature: Add smart contract storage optimization with TTL management

[Smartdevs17]

Problem

Smart contract storage entries don't have explicit TTL (time-to-live) management. Soroban charges rent for persistent storage, and unused entries waste funds.

Context

Efficient storage management reduces operational costs and keeps the contract lean.

Proposed Solution

1. Set appropriate TTLs for different data types
2. Implement cleanup functions for expired data
3. Use temporary storage for short-lived data (e.g., flash loan guards)
4. Use instance storage for frequently accessed globals

Acceptance Criteria

• Storage types chosen appropriately (temporary vs persistent vs instance)
• TTL set for all persistent entries
• Cleanup function for expired entries
• Tests verify TTL behavior

Technical Notes

• Files: All contract modules that use env.storage()
• Soroban storage types: temporary, persistent, instance

Constraints

• Must not delete data that's still needed

[drips-wave]

This issue has been added to the Stellar Wave Program and is worth 150 Points.

🧑‍💻 Interested in contributing? Apply to work on this issue on Drips Wave, earn points, and receive rewards.

Warning

Only applications submitted via the apply link above will be considered. Please do not apply by commenting on the issue or opening a PR directly.

🤠 Repo maintainers: You can manage this issue's Points and Complexity on your Maintainer Dashboard here. Please keep an eye on applications and respond quickly 💙

ℹ️ Learn more about Drips Wave