Improvements and fixes

The VPN services on the organization page are now visible to organization admins and moderators only.

• A VPN service can now be deleted while plants are still assigned to it, and the confirmation names the plants removed from it.
• In the plants table, a plant can now be removed from its VPN service through the VPN dialog.
• Adding a VPN service now asks for its client address, and editing one accepts a new WireGuard configuration file or replacement keys.
• Opening a device that has not yet reported a status no longer fails.