refactor: extract components and utilities to keep files under 210 lines

- Extract types to src/types/bookmarks.ts
- Extract utility functions to src/utils/bookmarkUtils.tsx
- Extract BookmarkItem component to src/components/BookmarkItem.tsx
- Extract BookmarkList component to src/components/BookmarkList.tsx
- Extract bookmark fetching logic to src/services/bookmarkService.ts
- Reduce main Bookmarks component from 416 to 100 lines
- Maintain all functionality while improving code organization
- Pass all linting and type checking

src/types/bookmarks.ts

@@ -0,0 +1,43 @@
+export interface ParsedNode {
+  type: string
+  value?: string
+  url?: string
+  encoded?: string
+  children?: ParsedNode[]
+}
+
+export interface ParsedContent {
+  type: string
+  children: ParsedNode[]
+}
+
+export interface Bookmark {
+  id: string
+  title: string
+  url: string
+  content: string
+  created_at: number
+  tags: string[][]
+  bookmarkCount?: number
+  eventReferences?: string[]
+  articleReferences?: string[]
+  urlReferences?: string[]
+  parsedContent?: ParsedContent
+  individualBookmarks?: IndividualBookmark[]
+}
+
+export interface IndividualBookmark {
+  id: string
+  content: string
+  created_at: number
+  pubkey: string
+  kind: number
+  tags: string[][]
+  parsedContent?: ParsedContent
+  author?: string
+  type: 'event' | 'article'
+}
+
+export interface ActiveAccount {
+  pubkey: string
+}