feat(db): Bun.SQL Kysely dialect for sqlite and postgres

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/db/src/migrations/index.ts

@@ -0,0 +1,4 @@
+import type { Migration } from "kysely/migration";
+
+/** All migrations, keyed by sortable name. Imported statically so bundles need no filesystem. */
+export const migrations: Record<string, Migration> = {};