build(android): Pin Kotlin JVM toolchain to 8 for compose

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: runningcode

sentry-compose/build.gradle.kts

@@ -15,6 +15,7 @@ plugins {
 }
 
 kotlin {
+  jvmToolchain(8)
   explicitApi()
 
   androidTarget {