Restructure documentation and add a first-backup quick start

[disaster123]

Summary

• replace the 860-line README with a concise, search-friendly project overview
• add a guided quick start through the first verified snapshot
• move the complete operational documentation into focused Markdown files under docs/
• add a documentation index and descriptive internal links
• document the current absence of a project license explicitly

Validation

• all generated Markdown files were read back from the branch and matched
• code fences, top-level headings, relative documentation links, and key safety/upgrade sections were checked
• CI should run the existing Python 3.11–3.13 test matrix