Feedback bar on every piece, not only on source pages

The feedback bar (read, star, vote, note, voice memo) exists on source pages only. Add it to stories, editions, history, maps and signals, keyed by the piece's path and the sha256 of its markdown, so a note is flagged when the piece changes.

Done when: data-fb is on every desk page; the reading list and "Copy for Claude" include them.