feat(dependencies): add rxdart package and improve string extension methods for better handling of empty strings and gender parsing

lib/core/utils/string_extentions.dart

@@ -1,11 +1,12 @@
 extension Capitalization on String {
   String capitalize() {
+    if (isEmpty) return '';
     return "${this[0].toUpperCase()}${substring(1).toLowerCase()}";
   }
 
   String parseGender() {
     if (this == 'male') {
-      return 'Мужской';
+      return 'Мужской';
     } else if (this == 'female') {
       return 'Женский';
     }