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/proxmox-backup-server.json

@@ -0,0 +1,44 @@
+{
+    "name": "Proxmox Backup Server (PBS)",
+    "slug": "proxmox-backup-server",
+    "categories": [
+        1
+    ],
+    "date_created": "2024-05-02",
+    "type": "ct",
+    "updateable": true,
+    "privileged": false,
+    "interface_port": 8007,
+    "documentation": "https://pbs.proxmox.com/docs/",
+    "website": "https://www.proxmox.com/en/proxmox-backup-server/overview",
+    "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/proxmox.webp",
+    "config_path": "",
+    "description": "Proxmox Backup Server is an enterprise backup solution, for backing up and restoring VMs, containers, and physical hosts. By supporting incremental, fully deduplicated backups, Proxmox Backup Server significantly reduces network load and saves valuable storage space.",
+    "install_methods": [
+        {
+            "type": "default",
+            "script": "ct/proxmox-backup-server.sh",
+            "resources": {
+                "cpu": 2,
+                "ram": 2048,
+                "hdd": 10,
+                "os": "debian",
+                "version": "13"
+            }
+        }
+    ],
+    "default_credentials": {
+        "username": "root",
+        "password": null
+    },
+    "notes": [
+        {
+            "text": "Set a root password if using autologin. This will be the PBS password. `passwd root`",
+            "type": "warning"
+        },
+        {
+            "text": "Advanced Install is only possible with IPv6 disabled! Otherwise, the installation may get stuck.",
+            "type": "warning"
+        }
+    ]
+}