[Draft] Add Firebase Crashlytics with Kermit log forwarding

[IanDBird]

Summary

• Integrate Firebase Crashlytics SDK for Android (Gradle plugins + BOM) and iOS (CocoaPods)
• Disable Crashlytics collection in debug builds on both platforms
• Add Kermit CrashlyticsLogWriter via expect/actual (androidMain, iosMain, wasmJsMain no-op) so all existing Logger injection sites automatically forward breadcrumbs and non-fatal exceptions to Crashlytics
• Initialize CrashKiOS on iOS for Kotlin/Native crash symbolication (guarded by AtomicBoolean)
• Add KermitLoggerTest covering severity mapping, tag forwarding, and min-severity filtering
• Add docs/firebase-crashlytics-setup.md with manual steps (Firebase Console, config files, dSYM upload, verification)

Prerequisites

• google-services.json must be placed at apps/android/google-services.json before Android builds will succeed
• GoogleService-Info.plist must be placed at apps/ios/App/GoogleService-Info.plist for iOS
• Run pod install in apps/ios after pulling this branch

Test plan

• iOS simulator tests pass (./gradlew :packages:core:logging:iosSimulatorArm64Test)
• Android build succeeds after adding google-services.json
• iOS build succeeds after pod install and adding GoogleService-Info.plist
• Verify Crashlytics breadcrumbs appear in Firebase Console after triggering a logged warning/error
• Verify non-fatal exceptions appear for logger.e(throwable = ex) { "..." } calls

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