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/lang/gmw/en-GB-scotland

@@ -0,0 +1,17 @@
+name English (Scotland)
+language en-gb-scotland
+language en 4
+
+maintainer Reece H. Dunn <msclrhd@gmail.com>
+status mature
+
+phonemes en-sc
+dictrules 2 5 6 7
+stressLength  180 130 200 200 0 0 250 270
+
+replace 03 @ V
+replace 03 I i
+replace 03 I2 i
+replace 01 aI aI2
+replace 02 a a/
+replace 02 u: U