e2e: replace stale post-login heading assertion with a URL wait

The shared signIn helper in every spec asserted
`getByRole("heading", { name: "Clawmates" })` after clicking Sign in, but
the dashboard's "Clawmates" is a decorative <span> in the top-bar logo,
not a heading — so all authenticated tests died on the same helper. Swap
that for `page.waitForURL((url) => !url.pathname.endsWith("/login"))`
with a 15s timeout. Robust across UI redesigns and doesn't couple the
signIn helper to a specific product surface. Should convert ~27 of the
remaining 30 failures to passes.

frontend/tests/e2e/p8-topology.spec.ts

@@ -11,7 +11,7 @@ async function signIn(page: Page) {
   await page.getByLabel("Email address").fill(OWNER_EMAIL);
   await page.getByLabel("Password").fill(OWNER_PASSWORD);
   await page.getByRole("button", { name: "Sign in" }).click();
-  await expect(page.getByRole("heading", { name: "Clawmates" })).toBeVisible();
+  await page.waitForURL((url) => !url.pathname.endsWith("/login"), { timeout: 15000 });
 }
 
 test("browse the topology catalog and build a graph", async ({ page }) => {