fix: use parent event timestamp for bookmarks instead of placeholder

- Add parentCreatedAt parameter to processApplesauceBookmarks function
- Replace all Math.floor(Date.now() / 1000) placeholders with parentCreatedAt || 0
- Update all call sites in bookmarkProcessing.ts to pass evt.created_at
- Individual bookmarks now inherit timestamp from their bookmark list event
- Bookmarks without valid parent timestamp will show as 0 (epoch) and be filtered by hideBookmarksWithoutCreationDate setting
- Eliminates 'now' placeholder timestamps in bookmark sidebar

src/utils/bookmarkUtils.tsx

@@ -121,36 +121,11 @@ export function hasContent(bookmark: IndividualBookmark): boolean {
 // Check if bookmark has a real creation date (not "Now" / current time)
 export function hasCreationDate(bookmark: IndividualBookmark): boolean {
   if (!bookmark.created_at) return false
-  
-  // For web bookmarks (kind 39701), they always have real timestamps from events
-  if (bookmark.kind === 39701 || bookmark.sourceKind === 39701) {
-    return true
-  }
-  
-  // If bookmark has no content, it likely failed to hydrate and its timestamp is a placeholder
-  const hasContent = bookmark.content && bookmark.content.trim().length > 0
-  if (!hasContent) {
-    return false
-  }
-  
-  // Check for URL-only bookmarks (synthetic bookmarks from NIP-51 processing)
-  // These get placeholder timestamps and should be filtered if they haven't been properly hydrated
-  const contentIsUrl = /^https?:\/\//i.test(bookmark.content.trim())
-  const hasMinimalTags = !bookmark.tags || bookmark.tags.length <= 1
-  
-  // If content is just a URL and there are minimal tags, this is likely an unhydrated reference
-  // These bookmarks are created with placeholder timestamps during NIP-51 processing
-  if (contentIsUrl && hasMinimalTags) {
-    // Additionally check if the ID suggests it's a synthetic bookmark
-    const isSyntheticId = bookmark.id.startsWith('url-') || 
-                          bookmark.id.startsWith('hashtag-') ||
-                          /^[0-9a-f]{64}$/i.test(bookmark.id) === false && !bookmark.id.includes(':')
-    if (isSyntheticId) {
-      return false
-    }
-  }
-  
-  return true
+  // 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)