- db_sync: rename column author→node_id, open chats.db instead of sync file,
db_sync_instance_add takes table_name directly
- chat_core: remove CREATE TABLE msg_ch_*, remove on_db_sync_insert (74 lines),
remove fallback INSERT in submit_message, add minimal on_msg_inserted
for GUI notification only
- db_manager: update getMessages for new schema (parse JSON from data column),
fix ORDER BY to use author_signature instead of datahash,
update syncCursorNext to parse JSON
- si_register simplified: db_count from same table, no more msg vs sync gap