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-x-rp

@@ -0,0 +1,15 @@
+name English (Received Pronunciation)
+language en-gb-x-rp
+language en-gb  4
+language en 5
+
+maintainer Reece H. Dunn <msclrhd@gmail.com>
+status mature
+
+phonemes en-rp
+
+replace 00  o@  O@
+replace 03 I i
+replace 03 I2 i
+replace 03 @ a#
+replace 03 3 a#