Add admin instance management and system tools

- Implemented sync_dev_hosts.sh for managing local hosts entries for development.
- Created admin_instances.html for managing school instances, including creation and listing.
- Developed admin_system.html for core services management, including restart and backup operations.
- Added my_instance.html for users to view and manage their assigned instances.
- Introduced provision_instance.sh for provisioning new instances with Docker, including Nginx configuration and SSL certificate handling.

Website/data/users.json

@@ -1,9 +0,0 @@
-[
-  {
-    "username": "Aiirondev",
-    "display_name": "Maximilian Gr\u00fcndinger",
-    "password_hash": "scrypt:32768:8:1$nfN2TTigH6GNrZig$548ac55b59b2c10f2730a4a45b4140c84eba33e2719f95175c05ab1f3a157959ff7a5d11c3d38bd2ea172b0143fa3a0e0e410b8bfcc81b8d91cfbbfc12b30399",
-    "is_admin": true,
-    "created_at": "2026-03-23T16:05:42Z"
-  }
-]