fix(dev): point TENANT_REGISTRY_URL at :8090

Unblock local dev: Keycloak owns :8080, so tenant-registry shifts to :8090. Prod is functionally unchanged.

Refs: M5.1

src/lib/tenant-registry.test.ts

@@ -48,7 +48,7 @@ describe("fetchTenantBySlug", () => {
     globalThis.fetch = fetchSpy;
     await fetchTenantBySlug("acme");
     expect(fetchSpy).toHaveBeenCalledWith(
-      "http://localhost:8080/v1/tenants/by-slug/acme",
+      "http://localhost:8090/v1/tenants/by-slug/acme",
       expect.any(Object),
     );
   });