Set JVM target to 1.8 for improved compatibility

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Pull request overview

This PR updates the Kotlin Multiplatform plugin module’s build configuration to explicitly compile JVM/Android bytecode for Java 8 (1.8), improving runtime compatibility with older JVM environments.

Changes:

• Bump plugin version from 3.1.0 to 3.1.1.
• Configure Kotlin jvm target to compile with jvmTarget = 1.8.

Comments suppressed due to low confidence (1)

plugin/build.gradle.kts:30

• Same as above: @Suppress("OPT_IN_USAGE") is a broad suppression. Consider opting in to the specific experimental Kotlin Gradle API instead (ideally once at file level) to keep other opt-in warnings visible and avoid repeating suppression blocks.

    androidTarget {
        publishLibraryVariants("release")
        @Suppress("OPT_IN_USAGE")
        compilerOptions {
            jvmTarget.set(JVM_1_8)
        }

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