Server Command Center: add subdomain + Cloudflare provisioning

- Migration: added subdomain, server_ip, server_port columns
- Seed: rewritten with hardcoded identifiers + full subdomain/IP/port data
  from Chronicler #87 audit (no more Pterodactyl API dependency)
- Route: POST /:id/provision-subdomain creates A + SRV records via
  Cloudflare API, saves subdomain to server_config
- Card: subdomain section shows FQDN if provisioned, provision button
  with inline input if not

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/arbiter-3.0/src/views/admin/servers/_server_card.ejs

@@ -74,6 +74,35 @@
         </div>
     </div>
 
+    <!-- Subdomain -->
+    <div class="mb-3" id="subdomain-<%= server.identifier %>">
+        <span class="text-gray-500 dark:text-gray-400 block text-xs mb-1">Subdomain</span>
+        <% if (config && config.subdomain) { %>
+            <div class="text-xs">
+                <span class="text-green-600 dark:text-green-400 font-mono">🌐 <%= config.subdomain %>.firefrostgaming.com</span>
+                <span class="text-gray-400 ml-2"><%= config.server_ip || '' %>:<%= config.server_port || 25565 %></span>
+            </div>
+        <% } else if (config && config.server_ip) { %>
+            <div class="text-xs">
+                <span class="text-gray-400">🌐 No subdomain</span>
+                <span class="text-gray-400 ml-2"><%= config.server_ip %>:<%= config.server_port || 25565 %></span>
+            </div>
+            <div class="flex items-center gap-2 mt-1">
+                <input type="text" name="subdomain" placeholder="e.g. stoneblock4"
+                       class="text-xs font-mono border border-gray-300 dark:border-gray-600 dark:bg-gray-800 dark:text-white rounded px-2 py-1 w-32"
+                       id="sd-input-<%= server.identifier %>">
+                <button hx-post="/admin/servers/<%= server.identifier %>/provision-subdomain"
+                        hx-include="#sd-input-<%= server.identifier %>"
+                        hx-target="#subdomain-<%= server.identifier %>"
+                        class="text-xs bg-purple-100 dark:bg-purple-900/30 text-purple-700 dark:text-purple-400 px-2 py-1 rounded hover:bg-purple-200 dark:hover:bg-purple-900/50">
+                    + Provision
+                </button>
+            </div>
+        <% } else { %>
+            <span class="text-gray-400 dark:text-gray-500 text-xs italic">No server config</span>
+        <% } %>
+    </div>
+
     <!-- Discord Channel Status -->
     <div class="mb-3">
         <span class="text-gray-500 dark:text-gray-400 block text-xs mb-1">Discord Channels</span>