feat(provider): add LaunchDarkly Remote Config provider

[kirich1409]

Goal

Implement RemoteConfigValueProvider backed by LaunchDarkly.

Rationale

LaunchDarkly is the market-leading SaaS feature-flag platform. Enterprise consumers commonly require first-party support before adopting a flag library.

Scope

LaunchDarkly does not ship a KMP SDK, so we split into two providers:

• providers:launchdarkly-android — wraps com.launchdarkly:launchdarkly-android-client-sdk (mirror providers/firebase/ shape).
• providers:launchdarkly-ios — wraps the LaunchDarkly Swift SDK via cinterop, exposed to common code through a thin Kotlin facade (similar packaging to providers/nsuserdefaults/).

Supported types: Boolean, String, Int, Long, Double, Float; enums by name.

References

• Interface: core/src/commonMain/kotlin/dev/androidbroadcast/featured/RemoteConfigValueProvider.kt
• KMP reference: providers/configcat/src/commonMain/kotlin/dev/androidbroadcast/featured/configcat/ConfigCatConfigValueProvider.kt
• Android-only reference: providers/firebase/src/main/kotlin/dev/androidbroadcast/featured/firebase/FirebaseConfigValueProvider.kt

Definition of Done

• New module(s) under providers/ published to Maven Central
• Unit tests with mocked LaunchDarkly client
• Sample wiring behind a build flag in sample/
• Wiki Providers page updated
• CHANGELOG.md [Unreleased] entry
• ./gradlew spotlessCheck && ./gradlew check clean