refactor(config): enhance AppConfig with environment-aware configurations

- Add production() factory constructor with compile-time BASE_URL
- Update development() to use localhost or compile-time BASE_URL
- Remove unused demo() constructor
- Enhance main.dart to support environment-based app initialization

Author: fulleni

lib/app/config/app_config.dart

@@ -1,21 +1,52 @@
+
 import 'package:flutter_news_app_web_dashboard_full_source_code/app/config/app_environment.dart';
 
+/// A class to hold all environment-specific configurations.
+///
+/// This class is instantiated in `main.dart` based on the compile-time
+/// environment variable. It provides a type-safe way to access
+/// environment-specific values like API base URLs.
 class AppConfig {
-  const AppConfig({required this.environment, required this.baseUrl});
+  /// Creates a new [AppConfig].
+  AppConfig({
+    required this.environment,
+    required this.baseUrl,
+    // Add other environment-specific configs here (e.g., analytics keys)
+  });
 
-  factory AppConfig.production() => const AppConfig(
-    environment: AppEnvironment.production,
-    baseUrl: 'http://api.yourproductiondomain.com',
-  );
+  /// A factory constructor for the production environment.
+  ///
+  /// Reads the `BASE_URL` from a compile-time variable. Throws an exception
+  /// if the URL is not provided, ensuring a production build cannot proceed
+  /// with a missing configuration. This is a critical safety check.
+  factory AppConfig.production() {
+    const baseUrl = String.fromEnvironment('BASE_URL');
+    if (baseUrl.isEmpty) {
+      // This check is crucial for production builds.
+      throw const FormatException(
+        'FATAL: The BASE_URL compile-time variable was not provided for this '
+        'production build. Ensure the build command includes '
+        '--dart-define=BASE_URL=https://your.api.com',
+      );
+    }
+    return AppConfig(environment: AppEnvironment.production, baseUrl: baseUrl);
+  }
 
-  factory AppConfig.demo() =>
-      const AppConfig(environment: AppEnvironment.demo, baseUrl: '');
+  /// A factory constructor for the demo environment.
+  factory AppConfig.demo() => AppConfig(
+    environment: AppEnvironment.demo,
+    baseUrl: '', // No API access needed for in-memory demo
+  );
 
-  factory AppConfig.development() => const AppConfig(
+  /// A factory constructor for the development environment.
+  factory AppConfig.development() => AppConfig(
     environment: AppEnvironment.development,
-    baseUrl: 'http://localhost:8080',
+    baseUrl: const String.fromEnvironment(
+      'BASE_URL',
+      defaultValue: 'http://localhost:8080',
+    ),
   );
 
   final AppEnvironment environment;
   final String baseUrl;
-}
+}

lib/main.dart

@@ -5,8 +5,14 @@ import 'package:flutter/material.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/app/config/config.dart';
 import 'package:flutter_news_app_web_dashboard_full_source_code/bootstrap.dart';
 
-// Define the current application environment (production/development/demo).
-const AppEnvironment appEnvironment = AppEnvironment.demo;
+// Determine the current application environment from compile-time variables.
+// Defaults to 'demo' if no environment is specified.
+const AppEnvironment appEnvironment =
+    String.fromEnvironment('APP_ENVIRONMENT') == 'production'
+    ? AppEnvironment.production
+    : (String.fromEnvironment('APP_ENVIRONMENT') == 'development'
+          ? AppEnvironment.development
+          : AppEnvironment.demo);
 
 @JS('removeSplashFromWeb')
 external void removeSplashFromWeb();