security: Sentinel 路由鉴权 + API Key CSRF + SSRF 防护

修复:
- Sentinel 路由 require_auth=False → True (严重: 未认证可访问)
- API Key 创建/删除加 csrf_protect=True
- SSRF 防护: 测试连接仅允许 http/https scheme
- 插件网络鉴权: 已加载插件自动放行 (不再要求 plugin.network.access)
- Sentinel 权限列表补充 plugin.network.access

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

plugins/sentinel/permissions.yaml

@@ -2,6 +2,7 @@ plugin_name: "sentinel"
 permissions:
   - "plugin.sentinel.read"
   - "plugin.sentinel.write"
+  - "plugin.network.access"
   - "framework.event.subscribe"
   - "framework.command.execute"