fix(dev): point TENANT_REGISTRY_URL default at :8090

Keycloak occupies :8080 in the dev stack; tenant-registry now defaults
to :8090. Update the portal's fallback base URL + .env.example +
the test that pins the URL it constructs.

Prod is unaffected — the Orca manifest sets TENANT_REGISTRY_URL via
service discovery (cross-VM), not a localhost port.

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),
     );
   });

src/lib/tenant-registry.ts

@@ -13,7 +13,7 @@ export type Tenant = {
 };
 
 function baseUrl(): string {
-  return process.env.TENANT_REGISTRY_URL ?? "http://localhost:8080";
+  return process.env.TENANT_REGISTRY_URL ?? "http://localhost:8090";
 }
 
 export async function fetchTenantBySlug(slug: string): Promise<Tenant | null> {