WatchOS: Add watchOS support with audio playback, custom swiftui dialog and shared code integration

Added watchOS support files & headers

What this does:

• Shares most code with iOS/tvOS (no duplication)
• Shares localizable.strings
• Custom SwiftUI dialogs since UIKit isn't available on watchOS

Key changes:

• watchOS(foundation) - Basic setup with proper headers
• watchOS(MediaLibrary) - Media library now works on watchOS
• watchOS(PlaybackService) - Audio playback (video disabled obviously)
• watchOS(AppCoordinator) - Specific AppCoordinator implementation for watchOS (instead of shared one)
• watchOS(ThumbnailCache) - Smaller cache for Watch constraints
• watchOS(CustomDialog) - SwiftUI dialogs for watchOS
• Build config updates

custom_swiftuidialog_final