refactor: keep Bookmarks.tsx under 210 lines by extracting logic

Extracted large functions into separate modules to follow DRY principles
and keep files manageable:

- Created useArticleLoader.ts hook (92 lines)
  - Handles article loading from naddr
  - Fetches article content and highlights
  - Sets up article coordinate for refresh

- Created contentLoader.ts utility (44 lines)
  - Handles both Nostr articles and web URLs
  - Unified content loading logic
  - Reusable across components

Result: Bookmarks.tsx reduced from 282 to 208 lines ✅

All files now under 210 line limit while maintaining functionality.

src/utils/contentLoader.ts

@@ -0,0 +1,44 @@
+import { nip19 } from 'nostr-tools'
+import { RelayPool } from 'applesauce-relay'
+import { fetchArticleByNaddr } from '../services/articleService'
+import { fetchReadableContent, ReadableContent } from '../services/readerService'
+
+export interface BookmarkReference {
+  id: string
+  kind: number
+  tags: string[][]
+  pubkey: string
+}
+
+export async function loadContent(
+  url: string,
+  relayPool: RelayPool,
+  bookmark?: BookmarkReference
+): Promise<ReadableContent> {
+  // Check if this is a kind:30023 article
+  if (bookmark && bookmark.kind === 30023) {
+    const dTag = bookmark.tags.find(t => t[0] === 'd')?.[1] || ''
+    
+    if (dTag !== undefined && bookmark.pubkey) {
+      const pointer = {
+        identifier: dTag,
+        kind: 30023,
+        pubkey: bookmark.pubkey,
+      }
+      const naddr = nip19.naddrEncode(pointer)
+      const article = await fetchArticleByNaddr(relayPool, naddr)
+      
+      return {
+        title: article.title,
+        markdown: article.markdown,
+        image: article.image,
+        url: `nostr:${naddr}`
+      }
+    } else {
+      throw new Error('Invalid article reference - missing d tag or pubkey')
+    }
+  } else {
+    // For regular URLs, fetch readable content
+    return await fetchReadableContent(url)
+  }
+}