AI-assisted Migration Pre-Flight Check: catch data-loss and lock risk before db push

TL;DR Add an AI-assisted "pre-flight check" that runs before supabase db push (CLI) or "Apply migration" (dashboard). It reads the pending migration, analyzes it against a ruleset plus AI review, and surfaces data-loss risks, lock-duration risks, and structural red flags *before* they hit production — not after. The scenario we keep hitting In production this is three separate foot-guns: 1. SET NOT NULL on a non-empty column does a full table scan under AccessExclusiveLock — every row must be validated, and every other query on orders blocks during it. 2. Adding NOT NULL + DEFAULT on a large table rewrites the whole table in Postgres < 11, and on modern versions still takes an exclusive lock. 3. DROP COLUMN legacy_code is destructive and irreversible once replication completes — no confirmation, no dry-run. The CLI and dashboard currently accept all of this without warning. supabase db push just applies it. Splinter catches *runtime* problem…