feat: Migrate from FreshCryptoLib to SmoothCryptoLib

[itasli]

Replace deprecated and unaudited FreshCryptoLib dependency with SmoothCryptoLib from same developpers, improves blockchain compatibility as well.

Changes

• Remove: FreshCryptoLib submodule and imports
• Add: SmoothCryptoLib submodule
• Update: Base64Url → OpenZeppelin Base64.encodeURL()
• Maintain: Identical API compatibility (no breaking changes)

Benefits

• Compatibility: Works on Polygon zkEVM and other chains without ModExp precompile
• Audits: Multiple security audits + partial formal verification

Compatibility

• API: Identical function signatures
• Tests: All existing tests pass
• Fallback: Maintains RIP-7212 precompile + library pattern

[cb-heimdall]

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