feat: Implement Flutter flavors for dev, stage, and prod environments with corresponding configurations and build scripts.

mobile-apps/apps/krow_staff/lib/app_config.dart

@@ -0,0 +1,13 @@
+enum Environment { dev, stage, prod }
+
+class AppConfig {
+  final Environment environment;
+  final String appTitle;
+  final String apiBaseUrl;
+
+  AppConfig({
+    required this.environment,
+    required this.appTitle,
+    required this.apiBaseUrl,
+  });
+}