refactor: separate voting delegation logic

[Grants268]

Summary

This PR separates the delegation-aware voting helper from the core voting module to keep the main voting file focused on core voting mechanics.

Changes

• removed the duplicate delegation module declaration in the contract module tree
• added a dedicated delegation-focused module for voting integration
• preserved the existing delegation-aware helper API while isolating it from the core vote implementation

Verification

• Repository diff reviewed and commit created locally.
• Full Cargo validation is not runnable in this environment because the Rust toolchain is not installed ().

closes #266
closes #268
closes #269
closes #267

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