Expose crypto profile on ConsensusEngine and use it in vote/authentication context

[aoxc]

Motivation

• Make the consensus engine crypto-agile by surfacing a per-engine crypto/profile identifier so authentication contexts derive network_id and signature_scheme from engine configuration instead of hardcoded values.
• Provide a public constructor to configure both network_id and signature_scheme at initialization time.
• Document roadmap and recommendations around crypto-agility and related engine design decisions.

Description

• Added a signature_scheme: u16 field to ConsensusEngine and threaded it through the engine state.
• Introduced ConsensusEngine::with_crypto_profile(state, network_id, signature_scheme) and updated new and with_network_id to call it with a default scheme of 1.
• Updated vote_authentication_context() to return network_id: self.network_id and signature_scheme: self.signature_scheme instead of hardcoded values.
• Added a unit test custom_crypto_profile_is_used_for_execution_certificate_context that constructs an engine with a custom crypto profile and asserts emitted execution certificate fields network_id and signature_scheme match the configured values.
• Extended the roadmap document docs/src/AOXCUNITY_ENGINE_ROADMAP_TR.md with sections on crypto-agility, evidence-first security, and recommended migration strategy (kept, not removed).

Testing

• Ran the crate unit tests including the new test custom_crypto_profile_is_used_for_execution_certificate_context with cargo test and all tests passed.
• Executed the consensus engine unit test suite covering certificate emission and finality and observed no regressions.

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Codex Task