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/iven

@@ -0,0 +1,14 @@
+language variant
+name Iven
+pitch  74 118
+formant 0 52 133 88
+formant 1 87 82 76
+formant 2 94 56 42
+formant 3 93 52 130
+formant 4 110 76 65
+formant 5  102 45 20
+formant 6  40 50 50
+formant 7 60 50 60
+formant 8 100 50 40
+voicing 530
+tone 600 255 1200 255 2000 160