test(audio-rooms): forward -DnestsInterop to test workers

Without this, `-DnestsInterop=true` on the Gradle command line was
only set on the Gradle JVM, not on the test executor JVM that
NostrNestsHarness.isEnabled() reads via System.getProperty. Result:
every interop test silently skipped no matter how the run was
invoked.

Also forwards `nestsInteropRev` (used by the harness to pin the
nostrnests revision in the cache).

Verified with `./gradlew :nestsClient:jvmTest --tests
NostrNestsAuthInteropTest -DnestsInterop=true` that the harness
now actually runs (the run only fails inside the test because the
sandbox blocks outbound traffic to GHCR / Docker Hub — both
registries return 503 at the auth-token endpoint, so we can't
pull strfry / build moq images here. On a network-enabled host
the harness will bring up the stack normally).

nestsClient/build.gradle.kts

@@ -86,3 +86,13 @@ kotlin {
         }
     }
 }
+
+// Forward the nostrnests interop opt-in property from the Gradle JVM
+// to test workers. Without this, `-DnestsInterop=true` on the Gradle
+// command line never reaches `NostrNestsHarness.isEnabled()` (which
+// reads it via `System.getProperty`), so every interop test silently
+// skips. See `nestsClient/src/jvmTest/.../interop/NostrNestsHarness.kt`.
+tasks.withType<Test>().configureEach {
+    System.getProperty("nestsInterop")?.let { systemProperty("nestsInterop", it) }
+    System.getProperty("nestsInteropRev")?.let { systemProperty("nestsInteropRev", it) }
+}