Invalidate prepared point cache on new setup

[moodlezoup]

No description provided.

[Copilot]

Pull request overview

This PR aims to prevent stale Arkworks prepared-point caching by invalidating the global prepared-point cache when a new setup is persisted, ensuring subsequent operations don’t accidentally reuse prepared points from an old setup.

Changes:

• Add invalidate_cache() to the Arkworks prepared-point cache implementation.
• Re-export invalidate_cache() from the Arkworks backend module when cache is enabled.
• Call invalidate_cache() after saving setups to disk (behind cfg(feature = "cache")).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/setup.rs	Invalidates Arkworks prepared-point cache after persisting a setup.
src/backends/arkworks/mod.rs	Re-exports invalidate_cache under the cache feature.
src/backends/arkworks/ark_cache.rs	Implements invalidate_cache() to clear the global prepared cache.

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[sagar-a16z]

lgtm!