feat: 添加布局和路由组件

lib/views/LoginPage.dart

@@ -0,0 +1,66 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widget_previews.dart';
+import 'package:go_router/go_router.dart';
+
+class LoginPage extends StatelessWidget {
+  const LoginPage({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: Text('登录')),
+      body: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.center,
+          children: [
+            const Text('登录', style: TextStyle(fontSize: 24)),
+            const SizedBox(height: 16),
+            Row(
+              children: [
+                Expanded(flex: 1, child: const Text('用户名：')),
+                const SizedBox(width: 8),
+                Expanded(
+                  flex: 4,
+                  child: TextField(
+                    decoration: const InputDecoration(hintText: '请输入用户名'),
+                  ),
+                ),
+              ],
+            ),
+            Row(
+              children: [
+                Expanded(flex: 1, child: const Text('密码：')),
+                const SizedBox(width: 8),
+                Expanded(
+                  flex: 4,
+                  child: TextField(
+                    decoration: const InputDecoration(hintText: '请输入密码'),
+                    obscureText: true,
+                  ),
+                ),
+              ],
+            ),
+
+            const SizedBox(height: 16),
+
+            ElevatedButton(
+              onPressed: () {
+                context.go('/home');
+              },
+              style: ElevatedButton.styleFrom(
+                minimumSize: const Size(double.infinity, 48),
+              ),
+              child: const Text('登录'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+// ========== 组件预览（顶层函数） ==========
+
+@Preview(name: 'LoginPage 默认状态')
+Widget loginPagePreview() => const LoginPage();