feat: Add mimalloc support and bump dependency versions

[wizrds]

Summary

This pull request updates dependencies across all crates in the lockbox project to address known CVEs and improve performance. It also modernizes development tooling, updates the Rust toolchain, and introduces optional mimalloc support for improved memory performance in container builds.

Changes Made

1. Bumped dependencies to latest versions across all crates to address security vulnerabilities and performance improvements.
2. Updated Rust toolchain from 1.90 to 1.94.
3. Modernized development tooling, including changelog generation and devcontainer configuration.
4. Replaced pre-commit with prek for development workflows.
5. Updated and expanded k6 load testing setup.
6. Added mimalloc feature flag and enabled it in the Docker image build.

Additional Notes

The mimalloc feature is optional and is currently enabled in the container build for performance evaluation.

Checklist

• Code follows project coding guidelines.
• Documentation reflects the changes made.
• Unit tests added or updated to cover the changes.