v1.1.5 of floaty_chatheads_ios

iOS implementation of floaty_chatheads with UIWindow-based PiP overlay, snap-to-edge physics, theming, and VoiceOver accessibility. Changelog excerpt: ### ⚡ Performance - **Migrated to Swift Concurrency (@MainActor).**Replaced @unchecked Sendableconformance and manual DispatchQueue.main.asyncdispatching with @MainActorisolation on the plugin class. All Pigeon API methods now have compile-time main-thread safety enforcement instead of runtime GCD checks. - Marked register(with:)as nonisolatedwith MainActor.assumeIsolatedfor Flutter registrar compatibility. ### 🐛 Bug Fixes - **Fixed chathead freeze during drag.**The `@MainActor[...]