Add About window with author and project information

- Added About menu item in application menu
- Created AboutView with app information
- Included author: Jia Xianhua
- Added GitHub project repository link
- Displays app version and description
- Added copyright information

Author: jiaxianhua

Hash/HashApp.swift

@@ -24,6 +24,85 @@ struct HashApp: App {
         .windowResizability(.contentSize)
         .commands {
             CommandGroup(replacing: .newItem) { }
+            CommandGroup(replacing: .appInfo) {
+                Button("About Hash") {
+                    showAboutWindow()
+                }
+            }
         }
     }
+    
+    private func showAboutWindow() {
+        let aboutWindow = NSWindow(
+            contentRect: NSRect(x: 0, y: 0, width: 400, height: 300),
+            styleMask: [.titled, .closable],
+            backing: .buffered,
+            defer: false
+        )
+        aboutWindow.title = "About Hash"
+        aboutWindow.center()
+        aboutWindow.isReleasedWhenClosed = false
+        
+        let aboutView = AboutView()
+        aboutWindow.contentView = NSHostingView(rootView: aboutView)
+        aboutWindow.makeKeyAndOrderFront(nil)
+    }
+}
+
+struct AboutView: View {
+    var body: some View {
+        VStack(spacing: 20) {
+            // App Icon
+            Image(systemName: "number.square")
+                .font(.system(size: 64))
+                .foregroundColor(.blue)
+            
+            // App Name and Version
+            VStack(spacing: 8) {
+                Text("Hash")
+                    .font(.title)
+                    .fontWeight(.bold)
+                
+                Text("Version 1.0.0")
+                    .font(.subheadline)
+                    .foregroundColor(.secondary)
+            }
+            
+            // Description
+            Text("A concise and efficient macOS hash calculation tool")
+                .font(.body)
+                .multilineTextAlignment(.center)
+                .padding(.horizontal)
+            
+            Divider()
+            
+            // Author and Project Info
+            VStack(spacing: 12) {
+                HStack {
+                    Text("Author:")
+                        .fontWeight(.medium)
+                    Spacer()
+                    Text("Jia Xianhua")
+                }
+                
+                HStack {
+                    Text("Project:")
+                        .fontWeight(.medium)
+                    Spacer()
+                    Link("GitHub Repository", destination: URL(string: "https://github.com/iOSDevLog/Hash")!)
+                        .foregroundColor(.blue)
+                }
+            }
+            .padding(.horizontal)
+            
+            Spacer()
+            
+            // Copyright
+            Text("© 2025 Hash Project Contributors")
+                .font(.caption)
+                .foregroundColor(.secondary)
+        }
+        .padding()
+        .frame(width: 400, height: 300)
+    }
 }