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/zabbix.json

@@ -0,0 +1,52 @@
+{
+  "name": "Zabbix",
+  "slug": "zabbix",
+  "categories": [
+    9
+  ],
+  "date_created": "2024-06-12",
+  "type": "ct",
+  "updateable": true,
+  "privileged": false,
+  "interface_port": null,
+  "documentation": "https://www.zabbix.com/documentation/current/en/manual",
+  "website": "https://www.zabbix.com/",
+  "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/zabbix.webp",
+  "config_path": "/etc/zabbix/zabbix_server.conf",
+  "description": "Zabbix is an all-in-one monitoring solution with a variety of enterprise-grade features available right out of the box.",
+  "install_methods": [
+    {
+      "type": "default",
+      "script": "ct/zabbix.sh",
+      "resources": {
+        "cpu": 2,
+        "ram": 4096,
+        "hdd": 6,
+        "os": "debian",
+        "version": "13"
+      }
+    }
+  ],
+  "default_credentials": {
+    "username": "Admin",
+    "password": "zabbix"
+  },
+  "notes": [
+    {
+      "text": "Database credentials: `cat ~/zabbix.creds`",
+      "type": "info"
+    },
+    {
+      "text": "You can choose between Zabbix agent (classic) and agent2 (modern) during installation",
+      "type": "info"
+    },
+    {
+      "text": "For agent2 the PostgreSQL plugin is installed by default; all plugins are optional",
+      "type": "info"
+    },
+    {
+      "text": "If agent2 with NVIDIA plugin is installed in an environment without GPU, the installer disables it automatically",
+      "type": "info"
+    }
+  ]
+}