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>

config/permissions/granted_permissions.json

@@ -1,9 +1 @@
-{
-  "example_plugin": [
-    "framework.event.subscribe",
-    "framework.command.execute",
-    "plugin.example.execute",
-    "plugin.example.read",
-    "plugin.example.write"
-  ]
-}
+{}