Add DNS server configuration for Alpine Linux

cloud-init/user-data-alpine.yml.tftpl

@@ -15,10 +15,14 @@ users:
     ssh_authorized_keys:
       - ${ssh_key}
 
-# 3. apk repositories configuration
-# Pin the two repositories used on this homelab: edge/main + edge/community.
-# Written BEFORE package_update/package_upgrade so apk uses this config immediately.
+# 3. Base system files (DNS + apk repos, written before package_update)
+# Alpine has no netplan/systemd-resolved, so we write resolv.conf ourselves.
 write_files:
+  - path: /etc/resolv.conf
+    owner: root:root
+    permissions: '0644'
+    content: |
+      nameserver ${dns_server}
   - path: /etc/apk/repositories
     owner: root:root
     permissions: '0644'