feat(userfront): improve magic link approval UX on mobile

- Fixes issue #852 where 'verify_failed' error was shown on remote approval
- Added specialized success view for remote-originated approval requests
- Added 'Close Window' action for mobile browsers
- Improved error handling for already verified/used tokens
- Added necessary i18n strings in Korean and English

userfront/lib/i18n_data.dart

@@ -645,6 +645,8 @@ const Map<String, String> koStrings = {
   "msg.userfront.login.token_missing": "로그인 토큰을 확인할 수 없습니다.",
   "msg.userfront.login.unregistered.body": "가입되지 않은 정보입니다.\\\\n회원가입 후 이용해 주세요.",
   "msg.userfront.login.verification.approved": "승인되었습니다. 로그인은 요청하신 창에서 완료됩니다.",
+  "msg.userfront.login.verification.approved_remote":
+      "승인되었습니다. 요청하신 브라우저 또는 PC 화면으로 돌아가 주세요.",
   "msg.userfront.login.verification.approved_local":
       "승인 되었습니다. 이 기기는 로그인되어 있는 상태입니다. 원격 창도 로그인이 될 예정입니다",
   "msg.userfront.login.verification.success": "로그인 승인에 성공했습니다.",
@@ -1914,8 +1916,10 @@ const Map<String, String> koStrings = {
   "ui.userfront.login.unregistered.action": "회원가입 하기",
   "ui.userfront.login.unregistered.title": "미등록 회원",
   "ui.userfront.login.verification.action_label": "확인",
+  "ui.userfront.login.verification.action_label_close": "창 닫기",
   "ui.userfront.login.verification.page_title": "로그인 승인",
   "ui.userfront.login.verification.title": "승인 완료",
+  "ui.userfront.login.verification.title_remote": "로그인 승인 완료",
   "ui.userfront.login_success.later": "나중에 하기 (대시보드로 이동)",
   "ui.userfront.login_success.qr": "QR 인증 (카메라 켜기)",
   "ui.userfront.login_success.title": "로그인 완료",
@@ -2777,6 +2781,8 @@ const Map<String, String> enStrings = {
       "We could not find an account for that information.\\\\\\\\\\\\\\\\nPlease sign up before continuing.",
   "msg.userfront.login.verification.approved":
       "Approved. Complete sign-in in the original window.",
+  "msg.userfront.login.verification.approved_remote":
+      "Approved. Please return to the original browser or PC screen.",
   "msg.userfront.login.verification.approved_local":
       "Approved. This device is already signed in, and the remote window will be signed in shortly.",
   "msg.userfront.login.verification.success": "Sign-in approval completed.",
@@ -4110,8 +4116,10 @@ const Map<String, String> enStrings = {
   "ui.userfront.login.unregistered.action": "Create an account",
   "ui.userfront.login.unregistered.title": "Account not found",
   "ui.userfront.login.verification.action_label": "Done",
+  "ui.userfront.login.verification.action_label_close": "Close Window",
   "ui.userfront.login.verification.page_title": "Sign-in approval",
   "ui.userfront.login.verification.title": "Approval complete",
+  "ui.userfront.login.verification.title_remote": "Sign-in approved",
   "ui.userfront.login_success.later": "Do this later (go to dashboard)",
   "ui.userfront.login_success.qr": "Use QR approval",
   "ui.userfront.login_success.title": "Sign-in complete",