Add a "Topics" tab to the Messages page so board members can start a
topic-scoped group conversation with management and their own-association
board members. Topic = predefined category + free-text subject; recipients
are multi-selected; replies are visible to all participants.
- New public tables message_threads / message_thread_participants /
thread_messages (migration board_topic_message_threads), added to the
realtime publication; RLS scopes reads/writes to thread participants via
is_thread_participant().
- create_topic_thread() RPC (SECURITY DEFINER) enforces recipient
eligibility server-side: management (admin/manager) or a board member of
the caller's own association; rejects anyone else.
- Frontend: messageTopics constant, useMessageThreads/useThreadMessages
hooks (realtime), TopicThreadList/TopicThreadView/NewTopicThreadDialog,
and a tabbed MessagesPage. Recipients notified via insert_notification
with a /dashboard/messages?thread= deep link. Existing 1:1 DMs unchanged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
