chore(android): bump detekt 1.23.8 -> 2.0.0-alpha.3 for Kotlin 2.3.21 + JDK 25

1.23.8 still failed on JDK 25 with "25.0.3" — same opaque shape as the
original Gradle 8.10 failure. The 1.23.x line bundles kotlin-compiler-
embeddable 1.9.10 which doesn't actually run on JDK 25 despite the
release note claim.

2.0.0-alpha.3 is explicitly built against Kotlin 2.3.21 + Gradle 9.3.1
+ tested with JDK 25 (per release notes). Alpha is acceptable risk
given there's no stable 2.x and we're already on bleeding-edge AGP 9
+ Kotlin 2.3 elsewhere.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/gradle/libs.versions.toml

@@ -31,7 +31,7 @@ turbine = "1.2.0"
 mockk = "1.13.13"
 compose-test = "1.7.5"
 ktlint-gradle = "12.1.1"
-detekt = "1.23.8"
+detekt = "2.0.0-alpha.3"
 
 [libraries]
 androidx-core-ktx = { module = "androidx.core:core-ktx", version = "1.13.1" }