Fix proof caching to speed up tests (#15)

[VagabondBushido]

Improve Test Performance with Proof Caching

This PR fixes issue #15 by adding a caching system for zero-knowledge proofs, significantly speeding up test execution.

🔧 What’s Changed?
• Introduced a ProofCache class to handle proof caching
• Integrated caching into the Node class
• Implemented automatic cache key generation based on proof inputs
• Ensured persistent caching across test runs
• Added a way to clear the cache when needed

🛠 New Features

✅ Auto-generates cache keys based on input parameters
✅ Stores proofs for faster reuse in future tests
✅ Supports clearing the cache when necessary
✅ Uses thread-safe file operations

✅ Testing & Results

Added unit tests to verify:
• Cache key consistency
• Proof storage & retrieval
• Proper handling of cache misses
• Cache clearing functionality

Performance Impact

The caching system improves test performance by:

• Avoiding redundant proof generation
• Persisting proofs between test runs
• Using efficient cache key generation

Additional Notes

• Cache is stored in a cache directory
• Cache keys are generated using SHA-256 hashing
• Cache can be cleared manually if needed

All tests pass successfully and show major performance gains for repeated operations

[Arinerron]

Thank you! Will review these PRs tomorrow morning.