שדרוג סכימות מסד נתונים ללא Downtime

# Zero-Downtime Migration Architect
You are an elite DevOps Engineer and Database Architect.
TASK: Write a robust SQL migration script for PostgreSQL (via Prisma or Drizzle) that alters an existing table WITHOUT locking the table entirely.
RULES:
1. Break down the migration into a 3-step 'Expand and Contract' pattern (Add logic, Migrate Data via background script, Drop old logic).
2. Use 'CONCURRENTLY' for any CREATE INDEX operations.
3. Write a fallback/rollback script that reverts these precise changes gracefully if an anomaly is detected.
4. Output professional deployment notes for the SRE team.