feat: Implement chat list and search functionality

- Added ChatListViewModel to manage chat list state and server search.
- Created ChatRowView for displaying individual chat rows.
- Developed SearchView and SearchViewModel for user search functionality.
- Introduced MainTabView for tab-based navigation between chats and settings.
- Implemented OnboardingPager for onboarding experience.
- Created SettingsView and SettingsViewModel for user settings management.
- Added SplashView for initial app launch experience.

Rosetta/Features/Onboarding/OnboardingPager.swift

@@ -0,0 +1,79 @@
+import SwiftUI
+
+/// UIPageViewController wrapper that handles paging entirely in UIKit.
+/// SwiftUI state is only updated after a page fully settles — zero overhead during swipe.
+struct OnboardingPager<Page: View>: UIViewControllerRepresentable {
+    @Binding var currentIndex: Int
+    let count: Int
+    let buildPage: (Int) -> Page
+
+    func makeCoordinator() -> Coordinator { Coordinator(self) }
+
+    func makeUIViewController(context: Context) -> UIPageViewController {
+        let vc = UIPageViewController(
+            transitionStyle: .scroll,
+            navigationOrientation: .horizontal
+        )
+        vc.view.backgroundColor = .clear
+        vc.dataSource = context.coordinator
+        vc.delegate = context.coordinator
+        vc.setViewControllers(
+            [context.coordinator.controllers[currentIndex]],
+            direction: .forward,
+            animated: false
+        )
+        // Make the inner scroll view transparent
+        for sub in vc.view.subviews {
+            (sub as? UIScrollView)?.backgroundColor = .clear
+        }
+        return vc
+    }
+
+    func updateUIViewController(_ vc: UIPageViewController, context: Context) {
+        context.coordinator.parent = self
+    }
+
+    // MARK: - Coordinator
+
+    final class Coordinator: NSObject, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
+        var parent: OnboardingPager
+        let controllers: [UIHostingController<Page>]
+
+        init(_ parent: OnboardingPager) {
+            self.parent = parent
+            // Create hosting controllers without triggering view loading
+            self.controllers = (0..<parent.count).map { i in
+                UIHostingController(rootView: parent.buildPage(i))
+            }
+        }
+
+        func pageViewController(
+            _ pvc: UIPageViewController,
+            viewControllerBefore vc: UIViewController
+        ) -> UIViewController? {
+            guard let idx = controllers.firstIndex(where: { $0 === vc }), idx > 0 else { return nil }
+            return controllers[idx - 1]
+        }
+
+        func pageViewController(
+            _ pvc: UIPageViewController,
+            viewControllerAfter vc: UIViewController
+        ) -> UIViewController? {
+            guard let idx = controllers.firstIndex(where: { $0 === vc }),
+                  idx < parent.count - 1 else { return nil }
+            return controllers[idx + 1]
+        }
+
+        func pageViewController(
+            _ pvc: UIPageViewController,
+            didFinishAnimating finished: Bool,
+            previousViewControllers: [UIViewController],
+            transitionCompleted completed: Bool
+        ) {
+            guard completed,
+                  let current = pvc.viewControllers?.first,
+                  let idx = controllers.firstIndex(where: { $0 === current }) else { return }
+            parent.currentIndex = idx
+        }
+    }
+}