feat(api): add article/attachment API endpoints, admin management, and API docs

- Articles API: list/detail/create/update/delete with source-based permission control
- Attachments API: upload/list/delete with source-based permission control
- ApiKeyInfo API: query current key permissions
- Admin ApiKey management: generate/regenerate/toggle/permission settings with layui UI
- Frontend API documentation page with complete interface reference

app/index/controller/ApiDoc.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace app\index\controller;
+
+use think\facade\View;
+
+class ApiDoc extends Common
+{
+    public function index()
+    {
+        $page_title = 'API 文档';
+        View::assign('page_title', $page_title);
+
+        return View::fetch();
+    }
+}