docs: replace postgresql operator with dedicated rds for keycloak

[pavlochaikivskyi]

Summary

Documents the migration of Keycloak's database from the PGO PostgreSQL Operator to a managed RDS instance, with support for both a dedicated Keycloak RDS and a shared CodeMie instance.

Changes

• Added Keycloak PostgreSQL instance to the infrastructure deployments overview and scripted deployments outputs
• Removed PostgreSQL Operator from all component tables, deployment dependency lists, and manual deployment guides
• Updated Keycloak installation steps to create the required Kubernetes secrets and pass the database hostname and mode via --set flags
• Updated container resource table to reflect Keycloak's database is now a managed service rather than a pod

Testing

• Tested locally with npm start
• All pages render correctly
• Images display properly
• Internal links work
• Sidebar navigation works

Quality Checks

• npm run check passes (typecheck + lint + commitlint)
• No MDX compilation errors
• No raw angle brackets (<text> must be `<text>`)
• Sidebar references document IDs (not filenames)
• Images stored locally next to content (not in static/img/)
• Commit messages follow Conventional Commits
• No secrets or credentials in documentation

[github-actions]

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