fix: move Logto to auth.localhost subdomain to avoid /assets path conflict

Logto's login page references /assets/* which conflicts with the SPA's
assets at the same path. Using Host-based routing (auth.localhost) gives
Logto its own namespace - all paths on that subdomain go to Logto,
eliminating the conflict. *.localhost resolves to 127.0.0.1 and is a
secure context.

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

ui/src/config.ts

@@ -22,7 +22,7 @@ export async function fetchConfig(): Promise<AppConfig> {
 
   // Fallback to env vars (Vite dev mode)
   cached = {
-    logtoEndpoint: import.meta.env.VITE_LOGTO_ENDPOINT || `http://${window.location.hostname}`,
+    logtoEndpoint: import.meta.env.VITE_LOGTO_ENDPOINT || `http://auth.${window.location.hostname}`,
     logtoClientId: import.meta.env.VITE_LOGTO_CLIENT_ID || '',
     logtoResource: import.meta.env.VITE_LOGTO_RESOURCE || '',
     scopes: [