v0.1.0: feat(gradle-plugin): auto-apply Kotlin Serialization compiler plugin

- Apply org.jetbrains.kotlin.plugin.serialization automatically so
  @Serializable works on client screen classes out of the box
- Same hasPlugin() guard as KSP: skips if consumer already declared it
- kotlinx-serialization-core is already exposed via navease-runtime api(),
  so the runtime dependency is covered transitively — zero boilerplate needed