🍱 Add app icon

✨ Multiple pages

lib/screens/about_page.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/material.dart';
+
+class AboutPage extends StatelessWidget {
+  const AboutPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('About')),
+      body: Padding(
+        padding: const EdgeInsets.all(16.0),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.center,
+          children: [
+            const SizedBox(height: 20),
+            Icon(
+              Icons.calculate,
+              size: 80,
+              color: Theme.of(context).colorScheme.primary,
+            ),
+            const SizedBox(height: 20),
+            Text(
+              '方程计算器',
+              style: Theme.of(context).textTheme.headlineMedium,
+              textAlign: TextAlign.center,
+            ),
+            const SizedBox(height: 10),
+            Text(
+              'Version 1.0.0',
+              style: Theme.of(context).textTheme.bodyLarge,
+              textAlign: TextAlign.center,
+            ),
+            const SizedBox(height: 20),
+            Text(
+              '这是一个用于求解方程和表达式的计算器应用。\n\n支持多种类型的数学计算，包括代数方程、表达式求值等。',
+              style: Theme.of(context).textTheme.bodyMedium,
+              textAlign: TextAlign.center,
+            ),
+            const SizedBox(height: 30),
+            Text(
+              '© 2025 Simple Math Calculator',
+              style: Theme.of(context).textTheme.bodySmall,
+              textAlign: TextAlign.center,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}