Remove the ark-circom dependency completely

[seemenkina]

Background

Currently, ark-circom is used for three primary purposes:

1. Zkey reading and parsing
2. Witness calculation
3. Groth16 proof calculation

Current Status

• We've already switched to calculating proofs using iden3
• Key parsing can be accomplished with alternative libraries. For now use ark-zkey approach, but it requires changes
• Witness calculation still needs to be addressed (example of usage: https://github.com/vacp2p/zerokit/blob/8a3e33be418ca6f66fa041c3fda475e24bb82268/rln/src/protocol.rs#L562-L570

Why Remove ark-circom?

The dependency introduces significant compatibility issues:

• We can't use version 0.1.0 due to outdated dependencies
• We can't use version 0.5.0 because it conflicts with newer versions of other ark libraries
• Our current approach (using master branch with loosened dependencies) depends on wasmer-wasix which lacks x32 system support. See their open issue : https://github.com/wasmerio/wasmer/issues/4227

Proposed Solution

Replace all remaining ark-circom functionality with alternative implementations:

• [x] Witness calculation: Already migrated to iden3 (see #273)
• [ ] Key parsing: Research and implement alternative libraries
• [ ] Proof calculation: Identify and implement replacement