Draft: feat: add isolation state tables for namespaces and organizations

Relates to issue #572150 (closed)

This MR was created by Duo in Session 1137085

Changes

• Create namespace_isolations table with foreign key to namespaces
• Create organization_isolations table with foreign key to organizations
• Add boolean isolated column with default false for both tables
• Add timestamp columns for tracking isolation state changes
• Implement corresponding ActiveRecord models with proper associations