fix: preserve service ID on subdomain change, accept localhost as IP

- serviceUrl() now checks service.url before falling back to buildServiceUrl(id)
- Service update no longer overwrites ID with the new subdomain
- Accept "localhost" as valid IP in service update validation
- Find services by ID or URL match when updating

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dashcaddy-api/routes/services.js

@@ -422,7 +422,7 @@ module.exports = function(ctx) {
       return ctx.errorResponse(res, 400, 'Invalid port number (must be 1-65535)');
     }
 
-    if (ip && !validatorLib.isIP(ip)) {
+    if (ip && ip !== 'localhost' && !validatorLib.isIP(ip)) {
       return ctx.errorResponse(res, 400, '[DC-210] Invalid IP address');
     }
 
@@ -473,7 +473,7 @@ module.exports = function(ctx) {
 
     if (await exists(ctx.SERVICES_FILE)) {
       await ctx.servicesStateManager.update(services => {
-        const serviceIndex = services.findIndex(s => s.id === oldSubdomain);
+        const serviceIndex = services.findIndex(s => s.id === oldSubdomain || s.url?.includes(oldSubdomain));
         if (serviceIndex !== -1) {
           const existing = services[serviceIndex];
           const finalPort = port || existing.port;
@@ -481,7 +481,7 @@ module.exports = function(ctx) {
 
           services[serviceIndex] = {
             ...existing,
-            id: newSubdomain,
+            // Keep the original ID — don't change it to the subdomain
             port: finalPort,
             ip: finalIp,
             tailscaleOnly: tailscaleOnly || false,