Agregar campo username a User entity y DTO

- Columna username (unique, nullable) en auth.users
- Campo username en CreateUserDto y UpdateUserDto

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tts/piper/espeak-ng-data/lang/zls/hr

@@ -0,0 +1,15 @@
+name Croatian
+language hr
+language hbs
+
+// attributes towards !variant3
+pitch 81 120
+formant 0 100 100 100
+formant 1  97  97 100
+formant 2  97  97 100
+formant 3  97 102 100
+formant 4  97 102 100
+formant 5  97 102 100
+
+stressAdd 10 10 0 0 0 0 -30 -30
+dictrules 1