`next build` imports lib/db.ts from several workers at once. On a fresh
machine they all saw an empty instruments table and raced to insert the
same symbols, failing the build with "UNIQUE constraint failed:
instruments.symbol". The emptiness check and the inserts now share one
IMMEDIATE transaction, and the insert is OR IGNORE as a backstop.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>