fix(update): concurrent apply reads as progress, not failure; idle-IO extraction

"Another update operation is already running" surfaced as a scary
failure while the update was in fact applying fine (OptiPlex, v1.7.118
rollout). The apply path now joins the in-flight install — same
overlay, same wait-for-new-version polling — and a concurrent download
attempt shows a calm in-progress note (EN+ES strings added). The
backend's tarball extractions run under ionice -c3 nice -n10 so a
200MB update can't starve podman/status calls into multi-minute
timeouts on small disks.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/locales/en.json

@@ -706,6 +706,8 @@
     "downloadFailed": "Download failed. Please try again.",
     "applySuccess": "Update applied. The service will restart momentarily.",
     "applyFailed": "Failed to apply update. You can try again or rollback.",
+    "applyInProgress": "An update is already being installed — hang tight, the node will restart when it finishes.",
+    "downloadInProgress": "An update download is already in progress — progress will appear above.",
     "rollbackSuccess": "Rolled back to previous version. Service will restart.",
     "rollbackFailed": "Rollback failed.",
     "pullAndRebuild": "Pull & Rebuild",

neode-ui/src/locales/es.json

@@ -693,6 +693,8 @@
     "downloadFailed": "La descarga fall\u00f3. Intente de nuevo.",
     "applySuccess": "Actualizaci\u00f3n aplicada. El servicio se reiniciar\u00e1 en un momento.",
     "applyFailed": "Error al aplicar la actualizaci\u00f3n. Puede intentar de nuevo o revertir.",
+    "applyInProgress": "Ya se est\u00e1 instalando una actualizaci\u00f3n \u2014 espere, el nodo se reiniciar\u00e1 al terminar.",
+    "downloadInProgress": "Ya hay una descarga de actualizaci\u00f3n en curso \u2014 el progreso aparecer\u00e1 arriba.",
     "rollbackSuccess": "Se revirti\u00f3 a la versi\u00f3n anterior. El servicio se reiniciar\u00e1.",
     "rollbackFailed": "Error al revertir.",
     "pullAndRebuild": "Pull y Recompilar",