Organize references by domain and normalize legacy docs

[antonflor]

What changed

• Moved all reference pages into a shallow docs/<domain>/<topic>.md hierarchy across networking, network platforms, Cisco contact center, cloud, containers, automation, Linux, high availability, and development.
• Kept project-level files (README.md, CONTRIBUTING.md, STYLE_GUIDE.md, and LICENSE) at the repository root.
• Added and documented a filename convention based on the canonical name engineers actually search for:
  • common, unambiguous acronyms stay short (tcp.md, ospf.md, lldp.md);
  • ambiguous concepts stay descriptive (spanning-tree.md, osi-model.md);
  • vendor references name the platform (arista-eos.md, cisco-ios.md, fortigate.md, junos.md);
  • domain-specific product acronyms omit redundant prefixes (cuic.md, cvp.md, icm.md).
• Rewrote visibly outdated or malformed legacy pages for Clos, LLDP, OSI, TCP, UDP, awk, sed, regex, SCP, and Corosync.
• Replaced the old Cisco CUIC/CVP/ICM pages with concise, version-sensitive legacy references that explicitly state technical validation is pending.
• Updated visual-guide links, contributor guidance, and the root index for every moved or renamed page.
• Reworked CI to discover every docs/**/*.md page automatically, enforce the shallow domain layout, reject topic Markdown at the root, require true H1 document titles, validate Mermaid blocks, and check internal links.

Why

The repository had outgrown a flat root-level collection. The README provided categories, but the filesystem did not. Several inherited pages also predated the current style guide and used heading level 3 as their document title, lacked honest validation status, or contained generic and stale prose.

Validation

• Built the restructure as one Git tree and one commit so unchanged pages retain their original blobs and GitHub can detect clean renames.
• Updated every index and visual-guide link alongside the moves.
• GitHub Actions will validate the resulting folder structure, H1 titles, Mermaid fences, and internal links before merge.