feat(system-metrics): implement system metrics API and frontend integration for CPU and RAM usage

[sophatvathana]

Summary

• feat(system-metrics): implement system metrics API and frontend integration for CPU and RAM usage

Changes

• workbench.rs

Testing

• cargo test
• cargo fmt --check
• Other (describe):

Checklist

• I updated relevant docs (README, CONTRIBUTING, etc.).
• I added tests or explained why they’re unnecessary.
• I verified CI passes locally or explained why it wasn’t run.

Screenshots / Notes (optional)

• Add screenshots, logs, or anything reviewers should see.