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/kaukovalta

@@ -0,0 +1,16 @@
+language variant 
+name Kaukovalta
+formant 0 80    80 100   
+formant 1 40 80 100     
+formant 2 70 100  130      
+formant 3 80    100 60    
+formant 4 70 90 100 
+formant 5 70  90  100  
+formant 6 70  100  90 
+   formant 7 100   90 110   
+formant 8 100   95 100 
+pitch 70 120 
+tone 100 130  800  130 2000  130 
+consonants 70 70      
+roughness 4
+