第二阶段已完成：统一插件平台已从“内置功能开关”扩展为可安装、签名校验、版本激活和回滚的插件系统。

主要成果：
- 新增独立插件 SDK：[PluginContracts.cs (line 11)](E:/jiaowu/src/Jiaowu.Plugin.Abstractions/PluginContracts.cs:11)
- 支持 RSA-PSS/SHA-256 签名插件包、Host API 兼容性和 ZIP 安全检查：[PluginPackageValidator.cs (line 14)](E:/jiaowu/src/Jiaowu.Api/Infrastructure/Plugins/PluginPackageValidator.cs:14)
- 支持暂存、待激活、重启装载、失败记录、版本回滚：[PluginPackageService.cs (line 32)](E:/jiaowu/src/Jiaowu.Api/Infrastructure/Plugins/PluginPackageService.cs:32)
- 插件可注册控制器、服务、数据库迁移、后台任务和事件处理器
- 外部插件 API 统一使用 /api/plugin-extensions/{pluginId}，并受启用状态中间件控制
- 插件中心新增 ZIP/SIG 上传、状态展示、激活、回滚和删除功能：[PluginsView.vue (line 212)](E:/jiaowu/web/src/views/PluginsView.vue:212)
- 提供可运行示例插件：[SamplePlugin.cs (line 10)](E:/jiaowu/samples/Jiaowu.SamplePlugin/SamplePlugin.cs:10)
- 提供打包签名脚本：[package-plugin.ps1](E:/jiaowu/scripts/package-plugin.ps1)
- 完整开发文档：[plugin-sdk.md (line 1)](E:/jiaowu/docs/plugin-sdk.md:1)
- 系统版本已调整为 3.0.0-beta1

samples/Jiaowu.SamplePlugin/Jiaowu.SamplePlugin.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+    <ProjectReference Include="..\..\src\Jiaowu.Plugin.Abstractions\Jiaowu.Plugin.Abstractions.csproj" />
+  </ItemGroup>
+</Project>

samples/Jiaowu.SamplePlugin/SamplePlugin.cs

@@ -0,0 +1,60 @@
+using Jiaowu.Plugin.Abstractions;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+
+namespace Jiaowu.SamplePlugin;
+
+public sealed class SamplePluginModule : IJiaowuPluginModule
+{
+    public void ConfigureServices(
+        IServiceCollection services,
+        IConfiguration configuration)
+    {
+        services.AddSingleton<SampleGreetingService>();
+    }
+}
+
+public sealed class SampleGreetingService
+{
+    public string BuildGreeting() => "签名示例插件已由宿主成功装载。";
+}
+
+[ApiController]
+[Authorize(Roles = "SuperAdmin")]
+[Route("api/plugin-extensions/sample.hello")]
+public sealed class SamplePluginController(SampleGreetingService greetings)
+    : ControllerBase
+{
+    [HttpGet("greeting")]
+    public IActionResult GetGreeting() => Ok(new { message = greetings.BuildGreeting() });
+}
+
+public sealed class SamplePluginMigration : IPluginDatabaseMigration
+{
+    public string PluginId => "sample.hello";
+    public string MigrationId => "001_initial";
+
+    public IReadOnlyList<string> GetStatements(PluginDatabaseProvider provider) =>
+        provider == PluginDatabaseProvider.Sqlite
+            ? ["CREATE TABLE IF NOT EXISTS SamplePluginNotes (Id TEXT NOT NULL PRIMARY KEY, Content TEXT NOT NULL);"]
+            : ["CREATE TABLE IF NOT EXISTS `SamplePluginNotes` (`Id` char(36) NOT NULL, `Content` varchar(500) NOT NULL, PRIMARY KEY (`Id`)) CHARACTER SET utf8mb4;"];
+}
+
+public sealed class SamplePluginBackgroundTask(
+    ILogger<SamplePluginBackgroundTask> logger) : IPluginBackgroundTask
+{
+    public string PluginId => "sample.hello";
+    public string Name => "sample-heartbeat";
+    public TimeSpan Interval => TimeSpan.FromHours(1);
+
+    public Task ExecuteAsync(
+        IServiceProvider services,
+        CancellationToken cancellationToken)
+    {
+        logger.LogInformation("示例插件后台任务正常运行。");
+        return Task.CompletedTask;
+    }
+}

samples/Jiaowu.SamplePlugin/plugin.json

@@ -0,0 +1,14 @@
+{
+  "id": "sample.hello",
+  "name": "示例问候插件",
+  "description": "演示插件 SDK、受保护 API、数据库迁移和后台任务。",
+  "version": "1.0.0",
+  "publisherId": "school-it",
+  "hostApiVersion": "1",
+  "category": "示例插件",
+  "backendAssembly": "backend/Jiaowu.SamplePlugin.dll",
+  "moduleType": "Jiaowu.SamplePlugin.SamplePluginModule",
+  "capabilities": [
+    "sample.greeting.read"
+  ]
+}