fix: remove deleted messages from shared media index to fix incorrect counts

[denfry]

Summary

• When saveDeletedMessages is on, messages are kept in memory via setDeleted() instead of destroy()
• destroy() goes through History::destroyMessage() which dispatches SharedMediaRemoveOne to update the Photos/Links/Files counts in the peer profile
• setDeleted() did not call removeFromSharedMediaIndex(), so deleted messages remained counted in the shared media totals
• The counts would only reset on app restart (when the in-memory items are gone)

Fix

Call removeFromSharedMediaIndex() at the end of setDeleted() so the shared media counts stay accurate when a message is marked as deleted.

Closes #174

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This PR was AI generated.