Complete iOS app UI with Liquid Glass design and fix login concurrency

[Kief5555]

This PR completes the iOS client UI using Apple's Liquid Glass design language and fixes critical thread-safety issues in the OAuth authentication flow.

Authentication & Store:

• Fixed silent login failures in OpenNOWStore.swift by annotating OAuthWebAuthenticator with @MainActor and hopping to the main actor for instantiation in GFNAPIClient.
• Added isBootstrapping published flag to OpenNOWStore to manage the splash screen state.
• Moved lastError = nil to the start of signIn() to ensure stale errors are cleared on sign-in attempts.

App Flow & Routing:

• Rewrote ContentView.swift to implement state-driven routing: SplashView → LoginView → MainTabView.
• Added shared design tokens (brandAccent, brandGradient) for consistent branding.

UI Implementation (Liquid Glass):

• Created LoginView with dark gradient background, ambient orbs, and glass-effect login card.
• Created HomeView with account summary, horizontal featured carousel, and adaptive game grid; exported GameCardView, GlassCardModifier, and ErrorBannerView for module reuse.
• Created BrowseView with searchable catalog and horizontal genre filter chips.
• Created LibraryView with specific states for signed-out users and empty libraries.
• Created SessionView with real-time telemetry charts (Swift Charts), status indicators, and session controls.
• Created SettingsView with grouped streaming preferences and account details.

Build Configuration:

• Added 6 new view files to project.pbxproj build phases and source groups.