TimelineViewModel: Deduplicate post URIs in notification fetching
Multiple notifications (likes, reposts, quotes) can reference the same
post, causing duplicate URIs in the getPosts batch request. This created
URLs too large for the 15s timeout. Add .distinct() to postsToFetch.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>