feat: wire up app root, navigation, and platform entry points

- Add App.kt root composable with state-based routing
  (Login -> Schedule -> EventDetail) driven by AuthViewModel.state
- Update MainActivity (Android), MainViewController (iOS), and
  Main.kt (Desktop) to host App() with their platform OAuthClient
- Add iOS Xcode source files (MyIceApp.swift, ContentView.swift)
  and Info.plist with myice:// URL scheme
- Delete Placeholder.kt
- Add kotlinx-coroutines-swing to desktopMain to provide
  Dispatchers.Main for viewModelScope (app crashed on desktop
  without it)

iosApp/iosApp/ContentView.swift

@@ -0,0 +1,10 @@
+import SwiftUI
+import ComposeApp
+
+struct ContentView: UIViewRepresentable {
+    func makeUIView(context: Context) -> some UIView {
+        MainViewControllerKt.MainViewController()
+    }
+
+    func updateUIView(_ uiView: UIViewType, context: Context) {}
+}

iosApp/iosApp/Info.plist

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>CFBundleDevelopmentRegion</key>
+    <string>$(DEVELOPMENT_LANGUAGE)</string>
+    <key>CFBundleExecutable</key>
+    <string>$(EXECUTABLE_NAME)</string>
+    <key>CFBundleIdentifier</key>
+    <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+    <key>CFBundleInfoDictionaryVersion</key>
+    <string>6.0</string>
+    <key>CFBundleName</key>
+    <string>$(PRODUCT_NAME)</string>
+    <key>CFBundlePackageType</key>
+    <string>$(PRODUCT_BUNDLE_PACKAGE_TYPE)</string>
+    <key>CFBundleShortVersionString</key>
+    <string>1.0</string>
+    <key>CFBundleVersion</key>
+    <string>1</string>
+    <key>LSRequiresIPhoneOS</key>
+    <true/>
+    <key>UIApplicationSceneManifest</key>
+    <dict>
+        <key>UIApplicationSupportsMultipleScenes</key>
+        <false/>
+    </dict>
+    <key>UILaunchScreen</key>
+    <dict/>
+    <key>UISupportedInterfaceOrientations</key>
+    <array>
+        <string>UIInterfaceOrientationPortrait</string>
+        <string>UIInterfaceOrientationLandscapeLeft</string>
+        <string>UIInterfaceOrientationLandscapeRight</string>
+    </array>
+    <key>UISupportedInterfaceOrientations~ipad</key>
+    <array>
+        <string>UIInterfaceOrientationPortrait</string>
+        <string>UIInterfaceOrientationPortraitUpsideDown</string>
+        <string>UIInterfaceOrientationLandscapeLeft</string>
+        <string>UIInterfaceOrientationLandscapeRight</string>
+    </array>
+    <key>CFBundleURLTypes</key>
+    <array>
+        <dict>
+            <key>CFBundleURLName</key>
+            <string>ch.parano.myice</string>
+            <key>CFBundleURLSchemes</key>
+            <array>
+                <string>myice</string>
+            </array>
+        </dict>
+    </array>
+</dict>
+</plist>

iosApp/iosApp/MyIceApp.swift

@@ -0,0 +1,11 @@
+import SwiftUI
+import ComposeApp
+
+@main
+struct MyIceApp: App {
+    var body: some Scene {
+        WindowGroup {
+            ContentView()
+        }
+    }
+}