Connected assistants page

Served on every tenant host that can sign users in. The signed-in user's connected MCP clients (name, verified host or unverified, approval date, last use, expiry) with a Disconnect button. A signed-out visitor is sent to the release's site.sign_in_path (else /auth/sign-in) with returnTo=/_run402/account/connections. On a *.run402.com host it answers 400 naming the app's *.run402.app page.