Include pet details in CommentModel serialization

Add a nested 'pets' object to CommentModel.toMap so serialized comments include the pet's name and profile image URL (mapped from petName and petProfileImageUrl). This allows downstream consumers to access basic pet info alongside the comment payload.

Author: syed-reza98

lib/models/post_model.dart

@@ -36,6 +36,10 @@ class CommentModel {
         'pet_id': petId,
         'text': text,
         'created_at': createdAt.toIso8601String(),
+        'pets': {
+          'name': petName,
+          'profile_image_url': petProfileImageUrl,
+        },
       };
 }