refactor: fix directory structure and namespaces for webman conventions

- Rename directories to lowercase: Controller→controller, Model→model, Service→service, Util→util, Bootstrap→bootstrap
- Update all namespaces from App\Xxx to app\xxx (webman convention)
- Update all import statements across the codebase
- Update route.php to use lowercase namespaces
- Remove unused CompanyFeishuApp model
- Comment out unimplemented controller routes

Following webman 2.x framework conventions:
- Models: app\model\{ClassName}
- Controllers: app\controller\{ClassName}
- Services: app\service\{ClassName}
- Utils: app\util\{ClassName}
- Middleware: app\middleware\{ClassName}

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/Controller/BaseController.php

@@ -1,41 +0,0 @@
-<?php
-
-namespace App\Controller;
-
-use Webman\Http\Request;
-use Webman\Http\Response;
-
-abstract class BaseController
-{
-    /**
-     * 成功响应
-     */
-    protected function success($data = null, string $message = 'success'): Response
-    {
-        return json([
-            'code' => 0,
-            'message' => $message,
-            'data' => $data,
-        ]);
-    }
-
-    /**
-     * 错误响应
-     */
-    protected function error(string $message = 'error', int $code = 1, $data = null): Response
-    {
-        return json([
-            'code' => $code,
-            'message' => $message,
-            'data' => $data,
-        ]);
-    }
-
-    /**
-     * 获取当前用户ID
-     */
-    protected function getUserId(Request $request): ?int
-    {
-        return $request->userId ?? null;
-    }
-}