arxsec-app: Operations & Runbooks

5 imported docs from arxsec-app.

Document	Repository	Source path
DEPLOYMENT_INVENTORY.md	arxsec-app	`DEPLOYMENT_INVENTORY.md`
Operator Runbook Index	arxsec-app	`docs/OPERATOR_RUNBOOK_INDEX.md`
Source Control Plane Operator Runbook	arxsec-app	`docs/source-control-plane-runbook.md`
Supabase Deployment Guide	arxsec-app	`SUPABASE_DEPLOYMENT_GUIDE.md`
Supabase Migration Deployment Guide	arxsec-app	`migrations/DEPLOYMENT_INSTRUCTIONS.md`