fix: use server code from webhook response for location select value

The stats webhook now returns a 'code' field (e.g. 'fr', 'usa')
alongside the display 'server' name. The option value now uses
s.code and falls back to slugified server name for backward compat.

add.html

@@ -564,10 +564,11 @@
             }
             servers.forEach(function(s) {
                 const server = s.server || '';
+                const serverCode = s.code || server.toLowerCase().replace(/\s+/g, '-');
                 const available = parseInt(s['Seats Available'], 10) || 0;
                 const label = server.charAt(0).toUpperCase() + server.slice(1);
                 const opt = document.createElement('option');
-                opt.value = server.toLowerCase().replace(/\s+/g, '-');
+                opt.value = serverCode;
                 if (available <= 0) {
                     opt.textContent = label + ' (sold out)';
                     opt.disabled = true;