fix/6131 stats page crash for archived projects

[royallsilwallz]

• Update working-groups.md
• fix: Move working-groups to docs after it got updated
• fix: Add updated docs from docs-old
• fix: Fix link to images
• fix: Move error_code.md to developers, migration.md to sysadmin
• fix: Remove erd.md
• fix: Delete old images that have been replace by the new diagrams
• fix: Remove doc that was already migrated and updated in docs
• fix: Fix relative links, add new docs to the menu
• fix: Add dataflow page for diagrams
• fix: Fix links to docs
• fix: For now make the index the about page
• fix: Adjust links for docs that got moved to developers directory
• fix: Fix links to images
• fix: Adjust links for docs that got moved to developers directory
• fix: Use hard word wrap for test editors
• fix: Move some docs to developers, add deep tech dive section
• Fix Project Stats page crash issue for archived projects