feat: Refactor UI components and improve animations for onboarding and authentication flows

Rosetta/Features/Onboarding/OnboardingPager.swift

@@ -1,9 +1,11 @@
 import SwiftUI
 
 /// UIPageViewController wrapper that handles paging entirely in UIKit.
-/// SwiftUI state is only updated after a page fully settles — zero overhead during swipe.
+/// Exposes both the settled page index AND a continuous drag progress for smooth dot tracking.
 struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
     @Binding var currentIndex: Int
+    /// Continuous progress: 0.0 = page 0, 1.0 = page 1, etc. Tracks the finger in real time.
+    @Binding var continuousProgress: CGFloat
     let count: Int
     let buildPage: (Int) -> Page
 
@@ -22,9 +24,13 @@ struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
             direction: .forward,
             animated: false
         )
-        // Make the inner scroll view transparent
+        // Hook into the inner scroll view for real-time offset tracking
         for sub in vc.view.subviews {
-            (sub as? UIScrollView)?.backgroundColor = .clear
+            if let scrollView = sub as? UIScrollView {
+                scrollView.backgroundColor = .clear
+                scrollView.delegate = context.coordinator
+                context.coordinator.pageWidth = scrollView.frame.width
+            }
         }
         return vc
     }
@@ -35,18 +41,28 @@ struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
 
     // MARK: - Coordinator
 
-    final class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
+    final class Coordinator: NSObject,
+        UIPageViewControllerDataSource,
+        UIPageViewControllerDelegate,
+        UIScrollViewDelegate
+    {
         var parent: OnboardingPager
         let controllers: [UIHostingController<Page>]
+        var pageWidth: CGFloat = 0
+        private var pendingIndex: Int = 0
 
         init(_ parent: OnboardingPager) {
             self.parent = parent
-            // Create hosting controllers without triggering view loading
+            self.pendingIndex = parent.currentIndex
             self.controllers = (0..<parent.count).map { i in
-                UIHostingController(rootView: parent.buildPage(i))
+                let hc = UIHostingController(rootView: parent.buildPage(i))
+                hc.view.backgroundColor = .clear
+                return hc
             }
         }
 
+        // MARK: DataSource
+
         func pageViewController(
             _ pvc: UIPageViewController,
             viewControllerBefore vc: UIViewController
@@ -64,6 +80,18 @@ struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
             return controllers[idx + 1]
         }
 
+        // MARK: Delegate
+
+        func pageViewController(
+            _ pvc: UIPageViewController,
+            willTransitionTo pendingVCs: [UIViewController]
+        ) {
+            if let vc = pendingVCs.first,
+               let idx = controllers.firstIndex(where: { $0 === vc }) {
+                pendingIndex = idx
+            }
+        }
+
         func pageViewController(
             _ pvc: UIPageViewController,
             didFinishAnimating finished: Bool,
@@ -75,5 +103,18 @@ struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
                   let idx = controllers.firstIndex(where: { $0 === current }) else { return }
             parent.currentIndex = idx
         }
+
+        // MARK: ScrollView — real-time progress
+
+        func scrollViewDidScroll(_ scrollView: UIScrollView) {
+            let w = scrollView.frame.width
+            guard w > 0 else { return }
+            // UIPageViewController's scroll view rests at x = width.
+            // Dragging left (next page) increases x; dragging right decreases.
+            let offsetFromCenter = scrollView.contentOffset.x - w
+            let fraction = offsetFromCenter / w
+            let progress = CGFloat(parent.currentIndex) + fraction
+            parent.continuousProgress = max(0, min(CGFloat(parent.count - 1), progress))
+        }
     }
 }