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/voices/!v/grandma

@@ -0,0 +1,17 @@
+language variant
+
+name grandma
+gender female 90
+pitch 120 230
+
+flutter 20
+formant 0 105 150 150
+formant 1 100 80 100
+formant 2 105 105 105
+formant 3 80 80 80
+formant 4 60 60 60
+formant 5 90 90 90
+formant 6 10 10 10
+formant 7 10 10 10
+formant 8 20 20 20
+voicing 50