refactor: remove frontend, move JSONs to json/ top-level

- Archive frontend to community-scripts/ProxmoxVE-Frontend-Archive
- Move frontend/public/json/ -> json/
- Update workflow paths in 5 actions:
  - update-versions-github.yml
  - update-json-date.yml
  - push-json-to-pocketbase.yml
  - delete-pocketbase-entry-on-removal.yml
  - autolabeler.yml
- Remove frontend-cicd.yml (no longer needed)
- Clean up .gitignore (remove frontend-specific entries)

json/urbackupserver.json

@@ -0,0 +1,44 @@
+{
+  "name": "UrBackup Server",
+  "slug": "urbackupserver",
+  "categories": [
+    7
+  ],
+  "date_created": "2025-01-18",
+  "type": "ct",
+  "updateable": true,
+  "privileged": true,
+  "interface_port": 55414,
+  "documentation": "https://www.urbackup.org/documentation.html",
+  "website": "https://www.urbackup.org/",
+  "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/urbackup.webp",
+  "config_path": "",
+  "description": "URBackup is an open-source backup software designed for creating reliable and efficient backups of both files and system images. It supports client-server architecture, allowing you to back up multiple computers to a central server. It offers features such as incremental backups, real-time file backup, and scheduling, ensuring minimal data loss and quick recovery",
+  "install_methods": [
+    {
+      "type": "default",
+      "script": "ct/urbackupserver.sh",
+      "resources": {
+        "cpu": 1,
+        "ram": 1024,
+        "hdd": 16,
+        "os": "debian",
+        "version": "13"
+      }
+    }
+  ],
+  "default_credentials": {
+    "username": null,
+    "password": null
+  },
+  "notes": [
+    {
+      "text": "You probably want to drastically extend the storage space to fit whatever clients you want to back up",
+      "type": "info"
+    },
+    {
+      "text": "Directory `/opt/urbackup/backups` is set as initial backup path. Change it to your liking",
+      "type": "info"
+    }
+  ]
+}