Fix broken links and update outdated references in documentation

Description

While reviewing the documentation, I noticed several broken external links and outdated references across the system design sections.

Proposed Changes

• Identify and update dead external links to active, official documentation or reliable archived mirrors.
• Verify and fix broken image path references.
• Ensure all hyperlinked resources comply with current repository standards.

Additional Context

I would like to work on resolving these broken links to keep the repository references accurate and up to date.