[Contract] Separate emergency guard guardian and admin roles

[abbaskachia]

Closes SoroLabs#634

Description

This PR refactors the Emergency Guard contract to introduce distinct role-based access control for Guardian and Admin responsibilities.

Changes

• Separated Guardian and Admin permissions.
• Added a dedicated Guardian role responsible for triggering emergency pause actions.
• Restricted unpause operations and administrative role management to the Admin role.
• Preserved existing initialization behavior while extending it to support explicit role-based initialization.
• Added/updated authorization logic to reflect the new role separation.

Related Issues

Testing & Verification Notes

Commands attempted:

cargo fmt --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test

Note: My local Windows environment is currently missing the MSVC linker (link.exe), which prevented running the full Rust test suite. The modified files were verified for formatting and editor diagnostics, and the project's CI will perform the complete validation.

Checklist

• Separated Guardian and Admin responsibilities.
• Guardian can trigger emergency pause.
• Admin controls unpause and role management.
• Existing initialization behavior remains compatible.
• Code formatted.
• Ready for review.