feat: refine archived habit management

frontend/src/lib/mvp-utils.ts

@@ -269,6 +269,25 @@ export function writeHabitGridCache<T>(week: string, habits: T[]) {
   habitGridCache = { week, habits }
 }
 
+export function invalidateHabitGridCache() {
+  habitGridCache = null
+}
+
+export async function performHabitRestore(actions: {
+  restore: () => Promise<unknown>
+  commitRestore: () => void
+  refreshGrid: () => Promise<boolean | unknown>
+}) {
+  await actions.restore()
+  actions.commitRestore()
+  try {
+    const refreshed = await actions.refreshGrid()
+    return { restored: true as const, refreshed: refreshed !== false }
+  } catch {
+    return { restored: true as const, refreshed: false }
+  }
+}
+
 export function readCountdownCache<T>() {
   if (!countdownCache) return null
   return { items: countdownCache.items as T[], archived: countdownCache.archived as T[] }
@@ -369,6 +388,22 @@ export function habitActionState(cell?: { scheduled?: boolean; paused?: boolean
   return { writable: true, reason: '' }
 }
 
+export type ArchivePanelState = 'idle' | 'loading' | 'success' | 'error'
+
+export function archivePanelFlags(state: ArchivePanelState, count: number) {
+  return {
+    loading: state === 'loading',
+    error: state === 'error',
+    empty: state === 'success' && count === 0,
+    list: state === 'success' && count > 0,
+  }
+}
+
+export function formatArchivedAt(value?: string | null, options: { timeZone?: string } = {}) {
+  const formatted = formatLocalShortDateTime(value, options)
+  return formatted === '未知时间' ? '归档时间未知' : `归档于 ${formatted}`
+}
+
 export function formatUserAgent(userAgent?: string | null): string {
   const ua = userAgent?.trim() ?? ''
   let device = '未知设备'