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/headscale.json

@@ -0,0 +1,44 @@
+{
+  "name": "Headscale",
+  "slug": "headscale",
+  "categories": [
+    4
+  ],
+  "date_created": "2024-05-13",
+  "type": "ct",
+  "updateable": true,
+  "privileged": false,
+  "interface_port": null,
+  "documentation": "https://headscale.net/",
+  "website": "https://github.com/juanfont/headscale",
+  "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/headscale.webp",
+  "config_path": "/etc/headscale/config.yaml",
+  "description": "An open source, self-hosted implementation of the Tailscale control server",
+  "install_methods": [
+    {
+      "type": "default",
+      "script": "ct/headscale.sh",
+      "resources": {
+        "cpu": 1,
+        "ram": 512,
+        "hdd": 2,
+        "os": "debian",
+        "version": "13"
+      }
+    }
+  ],
+  "default_credentials": {
+    "username": null,
+    "password": null
+  },
+  "notes": [
+    {
+      "text": "Configuration settings: `/etc/headscale/config.yaml`",
+      "type": "info"
+    },
+    {
+      "text": "Access headscale-admin UI via `http://<LXC-IP>/admin/`",
+      "type": "info"
+    }
+  ]
+}