feat(ui): 3-tab layout (Admin overview / My dashboard / Training) + Settings page

- App.vue: top tab bar (Admin overview [admin], My dashboard, Training) + Settings icon
- router: / = admin overview, /my/board, /training, /settings; non-admin '/' -> /my/board
- New views: Training.vue (pick ready product group -> personas), MyBoard.vue (win/lose +
  sessions summary), Settings.vue (change email/password, language)
- Backend: allow /api/me/board + /api/chat/sessions for any authenticated user (so the
  My dashboard tab works for admins too), not just 'user' role
- i18n EN/TH keys; rebuilt frontend/dist
Verified: build ok, /api/me/board + /api/chat/sessions + /api/groups all 200 for admin.

backend/app/api/chat_routes.py

@@ -168,7 +168,6 @@ def finish_session(gid: str, pid: str):
 
 @chat_bp.get("/sessions")
 @require_auth
-@require_roles("user")
 def my_sessions():
     s = _stores()
     uid = current_user()["id"]