Issue 1671: Bluesky reply duplication

[danguyf]

Issue: #1671

This addresses the case in the linked issue. (Listed in chronological order, bottom to top.)
Current: A, B->A
Desired: B->A

It also addresses reply chains.
Current: A, B->A, C->B
Desired: C->B->A

(I, personally, would prefer that replies were displayed in chronological order, e.g. A->B->C reading bottom to top, but that is not the current behavior of the Twitter and Mastodon feeds so I didn't change it.)

[Copilot]

Pull request overview

This PR fixes the Bluesky reply duplication issue where posts in a reply chain were shown both as standalone posts and as part of the chain. The fix ensures that only the leaf post of a reply chain is displayed, with all parent posts shown as part of that chain.

Changes:

• Modified the database cache mapper to build complete parent chains and filter out intermediate posts that appear as parents of other posts in the feed
• Updated the UI mapper to display all parents in a chain (reversed for chronological order) instead of only the immediate parent

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
shared/src/commonMain/kotlin/dev/dimension/flare/data/database/cache/mapper/Bluesky.kt	Refactored toDbPagingTimeline to build parent chain maps, identify duplicate parent posts, and filter them out; extracted processBlueskyFeedItem helper function
shared/src/commonMain/kotlin/dev/dimension/flare/ui/model/mapper/Bluesky.kt	Modified parent rendering to display all parents in the reference chain (reversed) instead of only the first parent

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[Tlaster]

I think there's still room for improvement, but not right now. LGTM!