feat(bookmarks): Add filter/view for annotated bookmarks

[ainergiz]

Summary

Add ability to filter or view only bookmarks that have annotations attached.

Context

Users can now annotate bookmarks with personal notes. However, there's no easy way to:

• See which bookmarks have annotations at a glance
• Filter the bookmarks list to show only annotated items
• Search through annotation text

Related: #136 (original annotation feature), #233 (cloud sync)

Current Behavior

• Bookmarks shown in chronological order
• No visual indicator of which bookmarks have annotations
• Must open each bookmark to see if it has an annotation

Expected Behavior

• Visual indicator (icon/badge) on bookmarks that have annotations
• Filter option to show "Only annotated" bookmarks
• Optionally: Search within annotation text

Potential Implementation

Visual Indicator

• Add annotation icon/badge to PostCard when hasAnnotation(tweetId) is true
• Files: src/components/PostCard.tsx, src/components/PostList.tsx

Filter Option

• Add filter toggle in BookmarksScreen header (e.g., a key to toggle)
• Filter bookmarks list using getAnnotatedTweetIds()
• Files: src/screens/BookmarksScreen.tsx

UI Mockup

Bookmarks                    [a] Annotated only: ON
─────────────────────────────────────────────────────
📝 Tweet with annotation...
   @user · 2h
   [annotation preview]

📝 Another annotated tweet...
   @user2 · 5h

Additional Context

The useAnnotations hook already exposes:

• hasAnnotation(tweetId) - check if tweet has annotation
• getAnnotatedTweetIds() - get all annotated tweet IDs
• getAnnotation(tweetId) - get annotation text

These can be used directly to implement the filter.