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/robert

@@ -0,0 +1,17 @@
+language variant
+name Robert
+
+pitch  65 115
+
+formant 0 85 108 100
+formant 1 95 110 60
+formant 2 97 90 50
+formant 3 101 50 50
+formant 4 110 65 55
+formant 5 110 60 65
+formant 6 110 60 65
+formant 7 100 0 100
+formant 8 100 0 100
+voicing 115
+consonants 110 120
+