Fix: Add storage TTL bump calls #7

[JHON12091986]

Fix: Add storage TTL bump calls #7

Problem

The TreasuryContract and VotingContract use env.storage().persistent() to store data, but no TTL bump calls exist. This means contribution history and vote records can be silently deleted by the network.

Solution

• Added extend_ttl calls after every persistent storage write.
• Added a bump_instance() utility to all contracts that extends instance storage TTL.
• Called bump_instance() at the start of every state-changing function.
• Documented the chosen TTL values in code comments.

Files Modified

• src/treasury.rs: Added TTL bump for persistent storage.
• src/voting.rs: Added TTL bump for persistent storage.
• src/lib.rs: Added bump_instance() utility.

Testing

• Verified that extend_ttl is called after every persistent storage write.
• Verified that instance storage is bumped at the start of every method.
• All existing tests still pass.

Closes #7