feat: Phase 2 — upgrade deps to null-safe, replace deprecated packages

- pubspec: bump all maintained deps to null-safe latest; flutter pub get resolves
- Remove 12 packages (0-ref or no null-safe): splashscreen, flappy_search_bar,
  searchable_dropdown, share, platform_detect, flutter_inappwebview, countdown,
  gender_selection, flutter_dash, smooth_star_rating, hovering, ffi
- Add flutter_rating_bar
- Keep discontinued-but-null-safe for now (Phase 5): pull_to_refresh, hive, catcher
- New null-safe custom components (API-compatible, callers change only imports):
  utils/countdown.dart, widgets/general/{hover_widget,gender_selection,
  smooth_star_rating,search_bar}.dart
- main.dart: drop dead SplashScreen _buildBody + _to field
- 23 consuming files: swap deprecated imports to local components

Null-safety migration + upgraded-API adaptation = Phase 3.

lib/main.dart

@@ -14,7 +14,6 @@ import 'pages/create_online_store_1.dart';
 import 'pages/download.dart';
 import 'pages/me.dart';
 import 'package:pull_to_refresh/pull_to_refresh.dart';
-import 'package:splashscreen/splashscreen.dart';
 // import 'package:uni_links/uni_links.dart';
 
 import 'constants.dart';
@@ -41,8 +40,6 @@ void main() {
 }
 
 class MyApp extends StatelessWidget {
-  String _to = '/';
-
   MyApp() {
     Routes.configure();
     Utils().init();
@@ -95,24 +92,6 @@ class MyApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
 
-    Widget _buildBody() {
-      return SplashScreen(
-        seconds: 5,
-        routeName: _to,
-        navigateAfterSeconds: Home(title: Constants.APP_TITLE,),
-        styleTextUnderTheLoader: new TextStyle(
-          fontWeight: FontWeight.bold,
-          fontSize: 20.0,
-        ),
-        imageBackground: (Image.network(Constants.BASE_API_URL + 'gallery/get-minimanager-splash/')).image,
-        backgroundColor: Colors.white,
-        onClick: () {
-
-        },
-        loaderColor: Colors.blue,
-      );
-    }
-
     return MaterialApp(
       debugShowCheckedModeBanner: Constants.DEBUG,
       navigatorKey: kIsWeb ? null : Catcher.navigatorKey,