docs: Convert Geo Mermaid diagrams to tables and lists

Relates to issue #583608 (closed)

Changes

This MR converts 7 problematic Mermaid diagrams in Geo documentation to simple tables and bulleted lists to resolve rendering issues with Mermaid v11.

Files Modified

1. doc/administration/geo/disaster_recovery/runbooks/planned_failover_multi_node.md

   • Replaced Mermaid diagram with bulleted lists showing Primary and Secondary site components
   • Primary Site (Multi-node): 6 nodes (Rails node 1, Rails node 2, PostgreSQL node, Gitaly node, Redis node, Monitoring node)
   • Secondary Site: 6 nodes (same components)

2. doc/administration/geo/disaster_recovery/runbooks/planned_failover_single_node.md

   • Replaced Mermaid diagram with bulleted lists
   • Primary Site: GitLab node
   • Secondary Site: GitLab node

3. doc/administration/geo/glossary.md (5 diagrams converted)

   • Single-node site section: Replaced diagram with descriptive text and bullet point
   • Multi-node site section: Replaced diagram with descriptive text and 3 bullet points (Application node, Database node, Gitaly node)
   • Geo deployment - Single-node sites: Replaced diagram with descriptive text and site sections
   • Geo deployment - Multi-node sites: Replaced diagram with descriptive text and site sections
   • Geo deployment - Mixed sites: Replaced diagram with descriptive text and three site sections

Benefits

• ✅ Fixes text cutoff issues in Mermaid v11
• ✅ Improves readability and accessibility
• ✅ Better format for static architecture information
• ✅ Easier to maintain
• ✅ All existing tables preserved