모바일 fallback 변경. .env유출 가능성 차단

userfront/lib/core/services/runtime_env.dart

@@ -1,9 +1,9 @@
-import 'package:flutter_dotenv/flutter_dotenv.dart';
-
 const _compileTimeEnv = {
   'APP_ENV': String.fromEnvironment('APP_ENV'),
+  'BACKEND_URL': String.fromEnvironment('BACKEND_URL'),
   'CLIENT_LOG_DEBUG': String.fromEnvironment('CLIENT_LOG_DEBUG'),
   'USERFRONT_DEBUG_LOG': String.fromEnvironment('USERFRONT_DEBUG_LOG'),
+  'USERFRONT_URL': String.fromEnvironment('USERFRONT_URL'),
 };
 
 String runtimeOriginFallback() {
@@ -13,17 +13,10 @@ String runtimeOriginFallback() {
       return origin;
     }
   } catch (_) {}
-  return 'https://sso-test.hmac.kr';
+  return '';
 }
 
 String envOrDefault(String key, String fallback) {
-  if (dotenv.isInitialized) {
-    final value = dotenv.env[key];
-    if (value != null && value.trim().isNotEmpty) {
-      return value;
-    }
-  }
-
   final compileTimeValue = _compileTimeEnv[key];
   if (compileTimeValue != null && compileTimeValue.trim().isNotEmpty) {
     return compileTimeValue;