feat: replace SharedPreferences with file-based AppConfigService and add HomePage navigation

- Implement AppConfigService using path_provider to store settings in a local JSON file,\n   ensuring configuration survives app updates/reinstalls.\n - Replace shared_preferences with AppConfigService in HomePage, SettingsPage,\n   and RegistrationPage.\n - Replace shared_preferences with AppConfigService in HomePage, SettingsPage,\n   and RegistrationPage.\n - Add HomePage.dart as the main navigation hub with feature cards (Registration,\n   Boxing, Shelf Query) and dynamic connection status bar.\n - Remove Settings entry from RegistrationPage; Settings are only accessible from\n   the Home page. Use 'flutter analyze' to verify the code.

lib/main.dart

@@ -1,5 +1,5 @@
 import 'package:flutter/material.dart';
-import 'package:pad_scanner/pages/registration_page.dart';
+import 'package:pad_scanner/pages/home_page.dart';
 
 void main() {
   runApp(const PadScannerApp());
@@ -11,12 +11,12 @@ class PadScannerApp extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
-      title: '上架登记',
+      title: 'CargoTrace',
       theme: ThemeData(
         colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
         useMaterial3: true,
       ),
-      home: const RegistrationPage(),
+      home: const HomePage(),
     );
   }
 }