feat: Aggregate friends' timelines into unified feed

[melvincarvalho]

Summary

Currently the app only shows posts from your own timeline. A true social feed should aggregate posts from friends.

Proposed Implementation

1. Read foaf:knows from user's WebID profile
2. Discover friend timelines via pim:storage or solid:timeline predicate
3. Fetch recent posts from each friend's /public/timeline/
4. Merge and sort all posts by date into unified feed

Considerations

• Request volume: Could be many HTTP requests (1 profile + N friends × M day files)
• Caching: Should cache friend profiles and posts with appropriate TTL
• Pagination: Load friends incrementally, not all at once
• Failures: Handle friends with no timeline or inaccessible pods gracefully
• Performance: Consider parallel fetching with concurrency limit
• Privacy: Only fetch from /public/ paths unless explicitly granted access

Data Available

User's profile already has foaf:knows triples:

<#me> foaf:knows <https://www.w3.org/People/Berners-Lee/card#i> .
<#me> foaf:knows <https://deiu.me/profile#me> .
# ... many more

UI Changes

• Add "My Posts" / "All Posts" toggle
• Show friend's avatar and name on their posts
• Maybe add a "Following" sidebar section

Future Enhancements

• WebSocket subscriptions for real-time friend updates
• "Follow" button on profiles
• Separate solid:follows predicate (vs foaf:knows)