fix(ui): render KeyRecoveryWizard into body portal to avoid layout margin

Modal now mounts at document.body level via svelte mount/unmount.
Extracted WizardContent.svelte for portal rendering.
Eliminates 32px margin from page layout wrapper
(max-w-7xl/space-y-6/px-4 container).

Added KeyRecoveryWizard as portal wrapper, WizardContent as
the actual modal component.

.env.example

@@ -26,7 +26,7 @@ AGENT_HOST_PORT=7860
 AUTH_SECRET_KEY=change-me-to-a-random-secret-32-chars-min
 # Fernet-ключ шифрования паролей подключений и API-ключей.
 # Сгенерировать: python3 -c "import base64,os; print(base64.urlsafe_b64encode(os.urandom(32)).decode())"
-ENCRYPTION_KEY=3YIxOr3_GFht9ZyjRQMqOdtuO1CKOj8Y9mpY89iMbZY=
+ENCRYPTION_KEY=D40dpvWPZxKd41jeaTHtEs2R7nwMVLxbkMRLjAICRls=
 # Сервисный токен для agent→backend вызовов.
 # Сгенерировать: python3 -c "import secrets; print('svc-' + secrets.token_urlsafe(24))"
 SERVICE_JWT=agent-service-secret