feat(app): Вынести инициализацию приложения за splash (#4)

Co-authored-by: PetrovY <y.petrov@friflex.com>

lib/features/splash/splash_screen.dart

@@ -0,0 +1,18 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/widgets.dart';
+import 'package:friflex_starter/gen/assets.gen.dart';
+
+/// {@template SplashScreen}
+/// Экран загрузки приложения.
+/// {@endtemplate}
+class SplashScreen extends StatelessWidget {
+  /// {@macro SplashScreen}
+  const SplashScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: Assets.lottie.splash.lottie(),
+    );
+  }
+}