fix: use bun-sqlite migrator instead of drizzle-kit push in Docker

drizzle-kit push depends on better-sqlite3 which isn't supported in
Bun, causing migrations to fail and the server to crash-loop in prod.
Replace with drizzle-orm/bun-sqlite/migrator that applies the existing
SQL migration files using the native bun:sqlite driver.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

entrypoint.sh

@@ -1,4 +1,4 @@
 #!/bin/sh
 set -e
-bun run db:push
+bun run src/db/migrate.ts
 exec bun run src/server/index.ts