Add app entry point

Sources/Photochk/PhotochkApp.swift

@@ -0,0 +1,25 @@
+import SwiftUI
+
+@main
+struct PhotochkApp: App {
+    @State private var model = ScanViewModel()
+
+    var body: some Scene {
+        WindowGroup {
+            ContentView(model: model)
+                .task { model.restorePreviousFolder() }
+        }
+        .defaultSize(width: 1120, height: 760)
+        .commands {
+            CommandGroup(replacing: .newItem) {
+                Button("フォルダを選ぶ…") { model.chooseFolder() }
+                    .keyboardShortcut("o", modifiers: .command)
+            }
+            CommandGroup(after: .toolbar) {
+                Button("再スキャン") { model.rescan() }
+                    .keyboardShortcut("r", modifiers: .command)
+                    .disabled(model.folder == nil || model.isScanning)
+            }
+        }
+    }
+}