feat: 实现 Blazor 前端界面 (Task 4.3) 和 CLI 工具 (Task 5.1)

Task 4.3 - Blazor 前端界面:
- 创建 CodePlay.WebUI Blazor Server 项目
- 实现 Converter.razor 代码转换页面
- 提供代码输入、语言选择、转换按钮
- 显示转换结果、TODO 列表和问题列表
- 更新导航菜单
- 注册 ConversionService 服务

Task 5.1 - CLI 命令行工具:
- 集成 System.CommandLine 库
- 实现 convert 命令（代码转换）
- 实现 list 命令（列出支持的转换）
- 实现 check 命令（检查是否支持）
- 支持 -s/-t 指定源/目标语言
- 支持 -i/-o 指定输入/输出文件
- 支持 -v 指定验证轮次
- 支持 -c 指定配置文件

测试:
- CLI help 命令: ✅
- CLI list 命令: ✅
- CLI convert 命令: ✅ (成功转换 C# 到 Java)
Co-authored-by: monkeycode-ai <monkeycode-ai@chaitin.com>

CodePlay.WebUI/Components/Pages/Weather.razor

@@ -0,0 +1,64 @@
+@page "/weather"
+@attribute [StreamRendering]
+
+<PageTitle>Weather</PageTitle>
+
+<h1>Weather</h1>
+
+<p>This component demonstrates showing data.</p>
+
+@if (forecasts == null)
+{
+    <p><em>Loading...</em></p>
+}
+else
+{
+    <table class="table">
+        <thead>
+            <tr>
+                <th>Date</th>
+                <th>Temp. (C)</th>
+                <th>Temp. (F)</th>
+                <th>Summary</th>
+            </tr>
+        </thead>
+        <tbody>
+            @foreach (var forecast in forecasts)
+            {
+                <tr>
+                    <td>@forecast.Date.ToShortDateString()</td>
+                    <td>@forecast.TemperatureC</td>
+                    <td>@forecast.TemperatureF</td>
+                    <td>@forecast.Summary</td>
+                </tr>
+            }
+        </tbody>
+    </table>
+}
+
+@code {
+    private WeatherForecast[]? forecasts;
+
+    protected override async Task OnInitializedAsync()
+    {
+        // Simulate asynchronous loading to demonstrate streaming rendering
+        await Task.Delay(500);
+
+        var startDate = DateOnly.FromDateTime(DateTime.Now);
+        var summaries = new[] { "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching" };
+        forecasts = Enumerable.Range(1, 5).Select(index => new WeatherForecast
+        {
+            Date = startDate.AddDays(index),
+            TemperatureC = Random.Shared.Next(-20, 55),
+            Summary = summaries[Random.Shared.Next(summaries.Length)]
+        }).ToArray();
+    }
+
+    private class WeatherForecast
+    {
+        public DateOnly Date { get; set; }
+        public int TemperatureC { get; set; }
+        public string? Summary { get; set; }
+        public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
+    }
+}