fix(hub): assert DB wipe and single-worker integration tests

Fail fast if TRUNCATE left Organization rows, drop the extra deleteMany
before seed create, and force vitest maxWorkers=1 so forks cannot race
the shared Postgres.

hub/vitest.config.ts

@@ -7,6 +7,7 @@ export default defineConfig({
     // concurrent truncate/insert races. Unit tests are fast either way.
     pool: "forks",
     fileParallelism: false,
+    maxWorkers: 1,
     env: { NODE_ENV: "test" },
   },
 });