Add onboarding, auth flow, design system and project structure

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Rosetta/DesignSystem/Components/LottieView.swift

@@ -0,0 +1,50 @@
+import SwiftUI
+import Lottie
+
+struct LottieView: UIViewRepresentable {
+    let animationName: String
+    var loopMode: LottieLoopMode = .playOnce
+    var animationSpeed: CGFloat = 1.5
+    var isPlaying: Bool = true
+
+    func makeUIView(context: Context) -> LottieAnimationView {
+        let animationView = LottieAnimationView(name: animationName)
+        animationView.contentMode = .scaleAspectFit
+        animationView.loopMode = loopMode
+        animationView.animationSpeed = animationSpeed
+        animationView.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
+        animationView.setContentCompressionResistancePriority(.defaultLow, for: .vertical)
+        if isPlaying {
+            animationView.play()
+        }
+        return animationView
+    }
+
+    func updateUIView(_ uiView: LottieAnimationView, context: Context) {
+        uiView.loopMode = loopMode
+        uiView.animationSpeed = animationSpeed
+
+        if isPlaying && !uiView.isAnimationPlaying {
+            uiView.play()
+        } else if !isPlaying {
+            uiView.stop()
+        }
+    }
+}
+
+// MARK: - Crossfading Lottie Container
+
+struct CrossfadingLottieView: View {
+    let animationName: String
+    let animationID: Int
+
+    var body: some View {
+        LottieView(
+            animationName: animationName,
+            loopMode: .playOnce,
+            animationSpeed: 1.5
+        )
+        .id(animationID)
+        .transition(.opacity.animation(.easeInOut(duration: 0.4)))
+    }
+}