Strip comments from backend and frontend source

Remove Go doc comments, TS/Svelte scaffold comments and explanatory
notes left over from the initial scaffold, plus a few leftover Spanish
notes in the compose file, SQL scripts and env template. Also drops
frontend/src/lib/index.ts, which only held the SvelteKit placeholder
comment and was never imported.

backend/.env.example

@@ -4,7 +4,6 @@ CORS_ALLOWED_ORIGINS=http://localhost:5173
 
 DATABASE_URL=postgres://dockermanager:dockermanager@localhost:5432/dockermanager?sslmode=disable
 
-# Se rellenan al configurar la aplicación OIDC en la consola de Zitadel (fase auth).
 ZITADEL_ISSUER=http://localhost:8081
 ZITADEL_CLIENT_ID=
 ZITADEL_CLIENT_SECRET=
@@ -15,5 +14,4 @@ S3_BUCKET=dockermanager
 S3_ACCESS_KEY=
 S3_SECRET_KEY=
 
-# Vacío = usar el socket Docker por defecto del sistema.
 DOCKER_HOST=