feat: add setting to hide bookmarks missing creation date

- Add hideBookmarksWithoutCreationDate to UserSettings
- New checkbox in Layout & Behavior settings
- Bookmarks without valid creation dates shown as 'Now'
- Setting disabled by default to maintain current behavior

src/components/BookmarkList.tsx

@@ -13,7 +13,7 @@ import { ViewMode } from './Bookmarks'
 import { usePullToRefresh } from 'use-pull-to-refresh'
 import RefreshIndicator from './RefreshIndicator'
 import { BookmarkSkeleton } from './Skeletons'
-import { groupIndividualBookmarks, hasContent, getBookmarkSets, getBookmarksWithoutSet } from '../utils/bookmarkUtils'
+import { groupIndividualBookmarks, hasContent, getBookmarkSets, getBookmarksWithoutSet, hasCreationDate } from '../utils/bookmarkUtils'
 import { UserSettings } from '../services/settingsService'
 import AddBookmarkModal from './AddBookmarkModal'
 import { createWebBookmark } from '../services/webBookmarkService'
@@ -100,6 +100,7 @@ export const BookmarkList: React.FC<BookmarkListProps> = ({
   // Merge and flatten all individual bookmarks from all lists
   const allIndividualBookmarks = bookmarks.flatMap(b => b.individualBookmarks || [])
     .filter(hasContent)
+    .filter(b => !settings?.hideBookmarksWithoutCreationDate || hasCreationDate(b))
   
   // Apply filter
   const filteredBookmarks = filterBookmarksByType(allIndividualBookmarks, selectedFilter)

src/components/Settings.tsx

@@ -41,6 +41,7 @@ const DEFAULT_SETTINGS: UserSettings = {
   paragraphAlignment: 'justify',
   syncReadingPosition: true,
   autoMarkAsReadOnCompletion: false,
+  hideBookmarksWithoutCreationDate: false,
 }
 
 interface SettingsProps {

src/components/Settings/LayoutBehaviorSettings.tsx

@@ -130,6 +130,19 @@ const LayoutBehaviorSettings: React.FC<LayoutBehaviorSettingsProps> = ({ setting
           <span>Automatically mark as read at 100%</span>
         </label>
       </div>
+
+      <div className="setting-group">
+        <label htmlFor="hideBookmarksWithoutCreationDate" className="checkbox-label">
+          <input
+            id="hideBookmarksWithoutCreationDate"
+            type="checkbox"
+            checked={settings.hideBookmarksWithoutCreationDate ?? false}
+            onChange={(e) => onUpdate({ hideBookmarksWithoutCreationDate: e.target.checked })}
+            className="setting-checkbox"
+          />
+          <span>Hide bookmarks missing a creation date</span>
+        </label>
+      </div>
     </div>
   )
 }

src/services/settingsService.ts

@@ -61,6 +61,8 @@ export interface UserSettings {
   // Reading position sync
   syncReadingPosition?: boolean // default: false (opt-in)
   autoMarkAsReadOnCompletion?: boolean // default: false (opt-in)
+  // Bookmark filtering
+  hideBookmarksWithoutCreationDate?: boolean // default: false
 }
 
 export async function loadSettings(

src/utils/bookmarkUtils.tsx

@@ -118,6 +118,16 @@ export function hasContent(bookmark: IndividualBookmark): boolean {
   return hasValidContent || hasId
 }
 
+// Check if bookmark has a real creation date (not "Now" / current time)
+export function hasCreationDate(bookmark: IndividualBookmark): boolean {
+  if (!bookmark.created_at) return false
+  // If timestamp is missing or equals current time (within 1 second), consider it invalid
+  const now = Math.floor(Date.now() / 1000)
+  const createdAt = Math.floor(bookmark.created_at)
+  // If created_at is within 1 second of now, it's likely missing/placeholder
+  return Math.abs(createdAt - now) > 1
+}
+
 // Bookmark sets helpers (kind 30003)
 export interface BookmarkSet {
   name: string