chore(db): drop branch migration ahead of staging merge

Both sides independently claimed idx 0271, so the snapshot and journal would
conflict add/add. Ours is plain additive DDL that drizzle regenerates from
schema.ts; staging's is a hand-written CONCURRENTLY index build that cannot be
regenerated. Dropping ours and re-generating on top of staging's is the only
order that preserves both.

schema.ts is deliberately untouched — it is the source of the regeneration.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: icecrasher321