chore: add rust-toolchain.toml to pin compiler version

[miguemagicdev]

Summary

This PR adds a rust-toolchain.toml file to the root directory to enforce a specific Rust toolchain version across all development environments and CI pipelines.

Why is this necessary?

For mission-critical software, we need reproducible builds. Relying on the user's default stable or nightly branch can lead to:

• Non-deterministic binaries: Different compiler versions can produce different machine code.
• Build failures: New lints in updated Rust versions can break CI unexpectedly.
• Subtle bugs: Rare regressions in the compiler or standard library could affect our production logic.

Changes

• Added rust-toolchain.toml pinned to version 1.85.0.
• Included the clippy and rustfmt components to ensure consistent linting and formatting across the team.

Impact

• Developers: Upon entering the directory, rustup will automatically detect the file and prompt/install the correct version.
• CI/CD: Pipelines will now use the version defined in this file, reducing configuration drift between the repository and the runner setup.

Verification Results

• Verified cargo build succeeds with the pinned version.
• Verified rustc --version matches the file definition.
• Confirmed CI picks up the toolchain automatically.