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/mike2

@@ -0,0 +1,12 @@
+language variant
+name Mike2
+klatt 6
+voicing 170
+pitch 67 107
+formant 1 95 100 100
+formant 2 95 100 100
+formant 3 105 100 100
+formant 4 115 100 100
+formant 5 115 100 100
+
+consonants 70 150