Refactor HTTPInterceptor and add CustomSnackBar helper

Refactor HTTPInterceptor to handle error responses and add a CustomSnackBar
helper to display snack bars. This will improve error handling and user
feedback in the application.

lib/utils/helpers/snack_bar.dart

@@ -0,0 +1,40 @@
+import 'package:flutter/material.dart';
+import 'package:syncrow_app/navigation/navigation_service.dart';
+
+class CustomSnackBar {
+  static displaySnackBar(String message) {
+    final key = NavigationService.snackbarKey;
+    if (key != null) {
+      final snackBar = SnackBar(content: Text(message));
+      key.currentState?.clearSnackBars();
+      key.currentState?.showSnackBar(snackBar);
+    }
+  }
+
+  static greenSnackBar(String message) {
+    final key = NavigationService.snackbarKey;
+    BuildContext? currentContext = key?.currentContext;
+    if (key != null && currentContext != null) {
+      final snackBar = SnackBar(
+        padding: const EdgeInsets.all(16),
+        backgroundColor: Colors.green,
+        content: Row(mainAxisAlignment: MainAxisAlignment.center, children: [
+          const Icon(
+            Icons.check_circle,
+            color: Colors.white,
+            size: 32,
+          ),
+          const SizedBox(
+            width: 8,
+          ),
+          Text(
+            message,
+            style: Theme.of(currentContext).textTheme.bodySmall!.copyWith(
+                fontSize: 14, fontWeight: FontWeight.w500, color: Colors.green),
+          )
+        ]),
+      );
+      key.currentState?.showSnackBar(snackBar);
+    }
+  }
+}