fix: rust-toolchain to toml

[LesnyRumcajs]

Fixes dependabot error

Dependabot can’t parse your rust-toolchain
Dependabot failed to update your dependencies because there was an error parsing the rust-toolchain found at /rust-toolchain.
Dependabot encountered the following error:only rust-toolchain files formatted as TOML are supported, the non-TOML format was deprecated by Rust

[Copilot]

Pull request overview

Converts the repository’s Rust toolchain specification to the TOML format so Dependabot can parse it and update Rust dependencies successfully.

Changes:

• Replaces the legacy rust-toolchain file with a TOML-based rust-toolchain.toml.
• Pins the Rust channel to 1.93.1 and declares required toolchain components.
• Removes the CARGO_REGISTRIES_CRATES_IO_PROTOCOL env override from CI.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
rust-toolchain.toml	Adds TOML-formatted toolchain config for Dependabot compatibility.
rust-toolchain	Removes deprecated non-TOML toolchain file.
.github/workflows/ci.yml	Simplifies CI env configuration by removing the crates.io protocol override.

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