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/benjamin

@@ -0,0 +1,11 @@
+language variant
+name Benjamin
+klatt 6
+consonants 70 70
+
+formant 1 101 100 130
+formant 2 102 100 100
+formant 3 100 100 100
+formant 4 100 100 100 470
+formant 5 100 100 100 350
+formant 6 100 100 100 100