feat(desktop): add encrypted DMs with split-pane layout (NIP-04/NIP-17)
Full desktop DM implementation with shared components extracted to commons:
- Relay layer: DM relay state, filter construction, subscription coordinator
- Shared: ChatroomFeedFilter, ChatroomFeedViewModel, ChatNewMessageState
- Shared UI: ChatBubbleLayout, ChatMessageCompose, ChatroomHeader, ChatTheme
- Desktop: split-pane (conversation list + chat), keyboard shortcuts, hover reactions
- IAccount extended with signer, sendNip04/17, chatroomList, isAcceptable
Refs: vitorpamplona/amethyst#1704
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
nrobi144
5d81da2486