e2e: add Marreta homepage-link regression test

16-marreta.spec.ts (standard project) asserts the user homepage's Marreta
open link actually reaches the Marreta app through the full guard chain
(Anubis PoW -> Authentik SSO -> app), and explicitly NOT the authentik
login flow. Guards the 2026-09-12 incident where marreta-proxy was created
without a linked Application, so the embedded outpost never loaded it and
the homepage link parked on a login wall.

Wires spec 16 into the standard project testMatch. Verified passing live.

tests/e2e/playwright.config.ts

@@ -24,7 +24,7 @@ export default defineConfig({
     },
     {
       name: "standard",
-      testMatch: /(10|12|13)-.*\.spec\.ts/,
+      testMatch: /(10|12|13|16)-.*\.spec\.ts/,
       use: { storageState: ".auth/qa-e2e.json" },
       dependencies: ["setup"],
     },