Add CoreDNS DNS server scripts

- ct/coredns.sh: CT script with update support
- install/coredns-install.sh: Install script with default Corefile
- json/coredns.json: JSON metadata

Closes #9665

json/coredns.json

@@ -0,0 +1,38 @@
+{
+    "name": "CoreDNS",
+    "slug": "coredns",
+    "categories": [5],
+    "date_created": "2026-03-27",
+    "type": "ct",
+    "updateable": true,
+    "privileged": false,
+    "interface_port": null,
+    "documentation": "https://coredns.io/manual/toc/",
+    "website": "https://coredns.io/",
+    "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/coredns.webp",
+    "config_path": "/etc/coredns/Corefile",
+    "description": "CoreDNS is a modern, lightweight, and highly extensible DNS server with a plugin-driven architecture. It is the default DNS engine for Kubernetes and ideal as a local authoritative DNS server for homelabs.",
+    "install_methods": [
+        {
+            "type": "default",
+            "script": "ct/coredns.sh",
+            "resources": {
+                "cpu": 1,
+                "ram": 256,
+                "hdd": 1,
+                "os": "Debian",
+                "version": "13"
+            }
+        }
+    ],
+    "default_credentials": {
+        "username": null,
+        "password": null
+    },
+    "notes": [
+        {
+            "text": "Configuration file is located at /etc/coredns/Corefile",
+            "type": "info"
+        }
+    ]
+}