refactor(frontend): extract NodeUpdatesModal and LocalUpdateConfirmDialog from FleetView (F5-2) (#916)

Moves the inline Node Updates dialog (~192 LOC), Local Update confirmation
dialog (~19 LOC), UpdateStatusBadge sub-component (~58 LOC), and shared
NodeUpdateStatus type into dedicated files under FleetView/. Shell drops
from 1,556 to 1,280 LOC.

Modal-local state (modalSearch, recheckingUpdates) and the
updatableRemoteCount derived value move into NodeUpdatesModal.

frontend/src/components/FleetView/LocalUpdateConfirmDialog.tsx

@@ -0,0 +1,34 @@
+import { Download } from 'lucide-react';
+import {
+    AlertDialog, AlertDialogAction, AlertDialogCancel, AlertDialogContent,
+    AlertDialogDescription, AlertDialogFooter, AlertDialogHeader, AlertDialogTitle,
+} from '@/components/ui/alert-dialog';
+
+interface LocalUpdateConfirmDialogProps {
+    open: boolean;
+    onOpenChange: (open: boolean) => void;
+    onConfirm: () => void;
+}
+
+export function LocalUpdateConfirmDialog({ open, onOpenChange, onConfirm }: LocalUpdateConfirmDialogProps) {
+    return (
+        <AlertDialog open={open} onOpenChange={onOpenChange}>
+            <AlertDialogContent>
+                <AlertDialogHeader>
+                    <AlertDialogTitle>Update local node?</AlertDialogTitle>
+                    <AlertDialogDescription>
+                        This will pull the latest Sencho image and restart the server. The dashboard will be
+                        briefly disconnected and will automatically reconnect when the update completes.
+                    </AlertDialogDescription>
+                </AlertDialogHeader>
+                <AlertDialogFooter>
+                    <AlertDialogCancel>Cancel</AlertDialogCancel>
+                    <AlertDialogAction onClick={onConfirm}>
+                        <Download className="w-4 h-4 mr-1.5" strokeWidth={1.5} />
+                        Update &amp; Restart
+                    </AlertDialogAction>
+                </AlertDialogFooter>
+            </AlertDialogContent>
+        </AlertDialog>
+    );
+}