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

- Move frontend/public/json/ to json/ (top-level)
- Update all workflow path references to json/
- Delete frontend-cicd.yml workflow
- Delete frontend/ directory entirely
- Clean up .gitattributes (remove frontend entries)

json/bak/centos.json

@@ -0,0 +1,40 @@
+{
+    "name": "CentOS Stream",
+    "slug": "centos",
+    "categories": [
+        2
+    ],
+    "date_created": "2025-12-04",
+    "type": "ct",
+    "updateable": true,
+    "privileged": false,
+    "interface_port": null,
+    "documentation": "https://docs.centos.org/",
+    "website": "https://www.centos.org/centos-stream/",
+    "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/centos.webp",
+    "config_path": "",
+    "description": "CentOS Stream is a continuously delivered Linux distribution that tracks just ahead of RHEL development. The upstream for the next RHEL release.",
+    "install_methods": [
+        {
+            "type": "default",
+            "script": "ct/centos.sh",
+            "resources": {
+                "cpu": 1,
+                "ram": 512,
+                "hdd": 4,
+                "os": "centos",
+                "version": "9"
+            }
+        }
+    ],
+    "default_credentials": {
+        "username": "root",
+        "password": null
+    },
+    "notes": [
+        {
+            "text": "CentOS Stream is the upstream development platform for RHEL.",
+            "type": "info"
+        }
+    ]
+}