feat: 增强管理员 API 鉴权，新增 token 有效天数配置，更新相关异常处理与错误码引用

tests/Feature/AdminAuthLoginTest.php

@@ -34,7 +34,7 @@ test('admin login returns bearer token when captcha passes validation', function
     ]);
 
     $resp->assertOk()
-        ->assertJsonPath('code', 0)
+        ->assertJsonPath('code', ErrorCode::Success->value)
         ->assertJsonPath('data.admin.username', 'tester')
         ->assertJsonPath('data.admin.nickname', '测试昵称')
         ->assertJsonStructure(['data' => ['token', 'token_type', 'admin' => ['id', 'username', 'nickname', 'email']]]);
@@ -52,7 +52,7 @@ test('admin captcha exposes key and image base64', function () {
     $resp = $this->getJson('/api/v1/admin/auth/captcha');
 
     $resp->assertOk()
-        ->assertJsonPath('code', 0);
+        ->assertJsonPath('code', ErrorCode::Success->value);
 
     $data = $resp->json('data');
     expect($data)->toBeArray()