feat(web): add Discord link to sidebar account menu

Add a "Join our Discord" entry to the account dropdown's external-links
group, opening https://discord.gg/wdNEHETs87 in a new tab. lucide-react
has no Discord brand glyph, so include a small inline Discord SVG icon
(brand color). Add the joinDiscord label to all 8 locales.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/i18n/locales/es-ES.ts

@@ -40,6 +40,7 @@ const esES = {
     helpDocs: 'Obtener ayuda',
     featureRequest: 'Solicitar función',
     starOnGitHub: 'Dar estrella en GitHub',
+    joinDiscord: 'Únete a Discord',
     create: 'Crear',
     edit: 'Editar',
     delete: 'Eliminar',