feat(frontend): implement AJAX no-refresh UX improvements (#276)

- Add dashboard auto-refresh with 5s polling and visibility-aware pause
- Harden node realtime reconnection with exponential backoff and polling fallback
- Implement local state patching for forward/tunnel/user mutations
- Add batch operation progress feedback UI
- Add shared list-state helpers for replace/remove operations
- Preserve derived UI state during server payload merges

Closes #276

Entire-Checkpoint: 7d6188355d7f

vite-frontend/src/utils/list-state.ts

@@ -0,0 +1,33 @@
+export const removeItemsById = <T extends { id: number }>(
+  items: T[],
+  ids: Iterable<number>,
+): T[] => {
+  const idSet = new Set(ids);
+
+  return items.filter((item) => !idSet.has(item.id));
+};
+
+export const replaceItemById = <T extends { id: number }>(
+  items: T[],
+  nextItem: T,
+): T[] => {
+  return items.map((item) => (item.id === nextItem.id ? nextItem : item));
+};
+
+export const upsertItemById = <T extends { id: number }>(
+  items: T[],
+  nextItem: T,
+  options?: { prepend?: boolean },
+): T[] => {
+  const existingIndex = items.findIndex((item) => item.id === nextItem.id);
+
+  if (existingIndex >= 0) {
+    return replaceItemById(items, nextItem);
+  }
+
+  if (options?.prepend) {
+    return [nextItem, ...items];
+  }
+
+  return [...items, nextItem];
+};