fix(hub): restore project create payload and stabilize integration DB seed

Explorer POST /projects was dropping projectId/folderId/workspaceDir after a
narrowed response shape, breaking admin-explorer. Make seedTestOrganization
idempotent under shared-DB isolation, force single-worker vitest, and align the
OAuth no-membership redirect expectation with authRoutes.

hub/test/integration/admin-auth.test.ts

@@ -242,7 +242,8 @@ describe("admin auth + org API guards", () => {
         headers: { cookie: `${OAUTH_STATE_COOKIE_NAME}=${nonce}` },
       });
       expect(res.statusCode).toBe(302);
-      expect(res.headers.location).toBe("/admin");
+      // New users without membership land on login error; session is still set.
+      expect(res.headers.location).toBe("/admin/login?error=no_organization");
       expect(JSON.stringify(res.headers["set-cookie"])).toContain("cph_session=");
 
       const user = await prisma.user.findUnique({ where: { feishuOpenId: "ou_new" } });