feat: add bookmark filter buttons by content type

- Add BookmarkFilters component with icon-based filter buttons
- Create bookmarkTypeClassifier utility for content type classification
- Filter bookmarks by article, video, note, or web types
- Apply filters across all bookmark lists (private, public, web, sets)
- Style filter buttons to match existing UI design

src/utils/bookmarkTypeClassifier.ts

@@ -0,0 +1,41 @@
+import { IndividualBookmark } from '../types/bookmarks'
+import { extractUrlsFromContent } from '../services/bookmarkHelpers'
+import { classifyUrl } from './helpers'
+
+export type BookmarkType = 'article' | 'video' | 'note' | 'web'
+
+/**
+ * Classifies a bookmark into one of the content types
+ */
+export function classifyBookmarkType(bookmark: IndividualBookmark): BookmarkType {
+  if (bookmark.kind === 30023) return 'article'
+
+  const isWebBookmark = bookmark.kind === 39701
+  const webBookmarkUrl = isWebBookmark ? bookmark.tags.find(t => t[0] === 'd')?.[1] : null
+  
+  const extractedUrls = webBookmarkUrl 
+    ? [webBookmarkUrl.startsWith('http') ? webBookmarkUrl : `https://${webBookmarkUrl}`] 
+    : extractUrlsFromContent(bookmark.content)
+  
+  const firstUrl = extractedUrls[0]
+  if (!firstUrl) return 'note'
+
+  const urlType = classifyUrl(firstUrl)?.type
+  
+  if (urlType === 'youtube' || urlType === 'video') return 'video'
+  if (urlType === 'article') return 'article'
+  
+  return 'web'
+}
+
+/**
+ * Filters bookmarks by type
+ */
+export function filterBookmarksByType(
+  bookmarks: IndividualBookmark[],
+  filterType: 'all' | BookmarkType
+): IndividualBookmark[] {
+  if (filterType === 'all') return bookmarks
+  return bookmarks.filter(bookmark => classifyBookmarkType(bookmark) === filterType)
+}
+