Custom workspace dropdown + Launch-Unreal button

Replace the ugly native <select> on the connect screen with a themed
custom dropdown (Select component). Add a Launch-Unreal button that appears
when the chosen working folder contains a .uproject: backend find_uproject
resolves the scope to disk and searches it (and one level down); the button
opens the project via the opener plugin. Bundled the UE icon (currentColor,
so white-on-dark / black-on-light per theme). New strings translated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/i18n.ts

@@ -67,6 +67,9 @@ const D: Record<string, Tr> = {
   "Get Latest": { ru: "Get Latest", de: "Get Latest", fr: "Get Latest", es: "Get Latest" },
   "Working…": { ru: "Работаю…", de: "Arbeite…", fr: "En cours…", es: "Trabajando…" },
   "pull from server": { ru: "забрать с сервера (pull)", de: "vom Server holen (pull)", fr: "récupérer du serveur (pull)", es: "traer del servidor (pull)" },
+  "Launch": { ru: "Запустить", de: "Starten", fr: "Lancer", es: "Iniciar" },
+  "Open this project in Unreal Engine": { ru: "Открыть проект в Unreal Engine", de: "Projekt in Unreal Engine öffnen", fr: "Ouvrir le projet dans Unreal Engine", es: "Abrir el proyecto en Unreal Engine" },
+  "Launching Unreal…": { ru: "Запуск Unreal…", de: "Unreal wird gestartet…", fr: "Lancement d’Unreal…", es: "Iniciando Unreal…" },
 
   // tabs / list
   "Changes": { ru: "Changes", de: "Änderungen", fr: "Modifications", es: "Cambios" },