docs: repair broken RustChain links and enforce CI checks

[genaaredes-ui]

Closes #16248
Closes #7910
Closes #7908
Closes #7886
Closes #7885
Closes #7792

Summary

• repair dead BCOS, tokenomics, mining, and stale DOI references across README and top-level docs
• add a compatibility page for the documented mining entry point
• add a dependency-free Python checker for relative Markdown and HTML links
• run the checker in the existing link-check workflow

Verification

• python tools/check_relative_links.py README.md docs — Checked 177 Markdown/HTML files; all local targets exist.
• python -m py_compile tools/check_relative_links.py
• git diff --check

[github-actions]

Welcome to RustChain! Thanks for your first pull request.

Before we review, please make sure:

• Non-doc PRs have a BCOS-L1 or BCOS-L2 label
• Doc-only PRs are exempt from BCOS tier labels when they only touch docs/**, *.md, or common image/PDF files
• New code files include an SPDX license header
• You've tested your changes against the live node

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