T14: Create migration for redaction_audit column

[dpaluy]

Task Details

Priority: p1 | Story Points: 1 | Group: D (Migration & Cleanup)
Depends on: T9

Files

• db/migrate/XXX_add_redaction_audit_to_interactions.rb

Acceptance Criteria

• Adds :text column (cross-database compatible)
• Model has attribute :redaction_audit, :json, default: {}
• Migration runs on SQLite, PostgreSQL, MySQL

Context

Part of PII Redaction Architecture Refactor - Phase 4: Migration & Cleanup
Plan Review Fix #3: Use :text instead of :jsonb for cross-DB support

See full plan: docs/plans/260106-02b-pii-redaction-architecture.md