refactor(admin): remove download config settings page and chain

- Drop the download config menu entry, route and schema from the settings SPA
- Remove the PHP schema section, the server-side alias validation and the
  reserved-alias list that only served that section
- Unregister aksrt_download_config from standalone import/export keys
- Drop the contract tests that locked the removed page; the Download.php
  runtime contracts stay untouched

src/Admin/Schema/SchemaPermissions.php

@@ -140,22 +140,6 @@ class SchemaPermissions {
                         ]],
                     ],
                 ],
-                'download' => [
-                    'key'        => 'download',
-                    'title'      => '下载配置',
-                    'version'    => '1.1.0',
-                    'option_key' => 'aksrt_download_config',
-                    'groups'     => [
-                        ['key' => 'basic', 'title' => '下载总开关', 'fields' => [
-                            ['key' => 'enabled', 'label' => '启用本站下载链接', 'type' => 'switch', 'default' => true, 'help' => '总开关：开启后下载通过本站中转链接（别名、次数、有效期生效）；关闭后下载按钮直接使用原始下载地址（直连），下方链接规则全部不生效，旧的中转链接同步失效。'],
-                        ]],
-                        ['key' => 'rules', 'title' => '链接规则', 'fields' => [
-                            ['key' => 'url_alias', 'label' => '下载链接 URL 别名', 'type' => 'input', 'default' => 'download', 'required' => true, 'dependsOn' => ['key' => 'enabled', 'value' => true], 'help' => '仅允许英文字母、数字、连字符和下划线；禁止中文、空格和 / \\ ? # & 等特殊符号。修改后旧别名路由立即失效，需重新获取下载地址。'],
-                            ['key' => 'default_max_uses', 'label' => '下载链接默认使用次数', 'type' => 'number', 'default' => 1, 'min' => 1, 'max' => 100, 'dependsOn' => ['key' => 'enabled', 'value' => true], 'help' => '单个链接可完成下载的次数；文件完整送达后才计次（HEAD 探测、传输中断不计次）。耗尽后链接返回 410，需重新获取。'],
-                            ['key' => 'ttl_minutes', 'label' => '下载链接默认有效期限（分钟）', 'type' => 'number', 'default' => 10, 'min' => 1, 'max' => 1440, 'dependsOn' => ['key' => 'enabled', 'value' => true], 'help' => '链接签发后超过该时长即失效并返回 410，不自动续期，需重新获取。'],
-                        ]],
-                    ],
-                ],
                 'moderation' => [
                     'key'        => 'moderation',
                     'title'      => '评论审核',

src/Admin/SchemaProvider.php

@@ -301,19 +301,6 @@ class SchemaProvider {
             }
         }
 
-        if ($domain === 'permissions' && $section === 'download') {
-            $alias = trim((string) ($data['url_alias'] ?? ''));
-            if ($alias === '') {
-                $errors[] = __('下载链接 URL 别名不能为空', 'aksrt');
-            } elseif (strlen($alias) > 48) {
-                $errors[] = __('下载链接 URL 别名长度不能超过 48 个字符', 'aksrt');
-            } elseif (!preg_match('/^[A-Za-z0-9_-]+$/', $alias)) {
-                $errors[] = __('下载链接 URL 别名只能包含英文字母、数字、连字符和下划线，禁止中文、空格和 / \\ ? # & 等特殊符号', 'aksrt');
-            } elseif (in_array(strtolower($alias), $this->reserved_download_aliases(), true)) {
-                $errors[] = __('该别名与系统保留路径冲突，请更换其他别名以避免路由 404', 'aksrt');
-            }
-        }
-
         return ['valid' => empty($errors), 'errors' => $errors];
     }
 
@@ -443,18 +430,6 @@ class SchemaProvider {
 			&& empty($parts['fragment']);
 	}
 
-    /**
-     * Top-level slugs that must never be shadowed by the download route.
-     */
-    private function reserved_download_aliases(): array {
-        return [
-            'wp-json', 'wp-admin', 'wp-content', 'wp-includes',
-            'admin', 'login', 'logout', 'register', 'lostpassword',
-            'feed', 'search', 'author', 'page', 'comments',
-            'sitemap', 'sign', 'cgi-bin',
-        ];
-    }
-
     public function read_settings(string $domain, string $section = ''): array {
         if ($section !== '') {
             $schema = $this->get_section_schema($domain, $section);

src/Settings/Settings.php

@@ -36,7 +36,6 @@ class Settings {
     public const STANDALONE_OPTION_KEYS = [
         'aksrt_captcha_config',
         'aksrt_moderation_config',
-        'aksrt_download_config',
         'aksrt_footer_tabbar',
         'aksrt_floating_buttons',
         'aksrt_credit_settings',