feat(pairing): auto-close the QR/link dialog once the device connects

The pairing session is single-use, so it leaving the pending list (polled
every 5s) means it was redeemed — close the dialog and toast success. Armed
only after the pairing has been seen in the pending list, so the stale list
at result-phase open can't blink the dialog shut; expired/cancelled sessions
close it silently. Pending-list polling now preserves the previous list on a
transient fetch failure instead of blanking it (which would also have faked
the redeem signal).

packages/ui/src/lib/i18n/messages/ja.settings.ts

@@ -296,6 +296,7 @@ export const settingsDict = {
   'settings.remoteInstances.clientAuth.addDevice.fallback.preferLocal': '可能なときは自宅の直接接続を優先',
   'settings.remoteInstances.clientAuth.addDevice.create': 'QRコードを作成',
   'settings.remoteInstances.clientAuth.addDevice.done': '完了',
+  'settings.remoteInstances.clientAuth.addDevice.connectedToast': 'デバイスを接続しました。',
   'settings.remoteInstances.clientAuth.pairingUrl': '接続リンク',
   'settings.remoteInstances.clientAuth.createdToken': 'この Token を今すぐコピーしてください。セキュリティのため、再表示されません。',
   'settings.remoteInstances.clientAuth.state.loading': 'Token を読み込み中...',