chore(ui): replace loading gif with birds animation and add loading text

packages/design_system/lib/src/loading/legacy_loading_indicator.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:sf_localizations/sf_localizations.dart';
 
 class LegacyLoadingIndicator extends StatelessWidget {
   final double size;
@@ -8,10 +9,23 @@ class LegacyLoadingIndicator extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Center(
-      child: Image.asset(
-        'packages/design_system/assets/animations/loading_legacy.gif',
-        width: size,
-        height: size,
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Image.asset(
+            'packages/design_system/assets/animations/birds_loading.gif',
+            width: size,
+            height: size,
+          ),
+          const SizedBox(height: 8),
+          Text(
+            context.translate(I18n.loadingText),
+            style: TextStyle(
+              fontSize: 14,
+              color: Theme.of(context).colorScheme.onSurfaceVariant,
+            ),
+          ),
+        ],
       ),
     );
   }