feat(playlists): act on the selected rows from the toolbar, and undo either

While rows are selected the toolbar's second row is the band: the count,
the last target as one click, Move to, Remove, Clear selection. Both write
in one request and undo back to the places; a video the target held before
stays there. Delete takes the selection when there is one. A failure puts
the rows back ticked.

A row's own move goes through the same write, so it undoes too, and the
single-row move route and service function are gone. A playlist row drops
its grip below a 24rem table: the row menu keeps the moves.

frontend/src/features/video/videoWrites.ts

@@ -59,11 +59,52 @@ export function removePlaylistItem(qc: QueryClient, list: ListRef, id: string) {
   });
 }
 
-/** Move a video from one playlist to another, in one request (see `api.moveToPlaylist`). */
-export function movePlaylistItem(qc: QueryClient, from: ListRef, id: string, to: ListRef) {
-  return api.moveToPlaylist(from.id, id, to.id).then((r) => {
-    markIfWatchLater(qc, from, id, false);
-    markIfWatchLater(qc, to, id, true);
+/** Take videos out of a playlist, in one request. */
+export function removePlaylistItems(qc: QueryClient, list: ListRef, ids: string[]) {
+  return api.removeManyFromPlaylist(list.id, ids).then((r) => {
+    for (const id of ids) markIfWatchLater(qc, list, id, false);
     return r;
   });
 }
+
+/** Put removed videos back at their places, in one request. */
+export function restorePlaylistItems(
+  qc: QueryClient,
+  list: ListRef,
+  ids: string[],
+  positions: number[],
+) {
+  return api.restoreToPlaylist(list.id, ids, positions).then((r) => {
+    for (const id of ids) markIfWatchLater(qc, list, id, true);
+    return r;
+  });
+}
+
+/** Move videos from one playlist to another, in one request (see `api.moveManyToPlaylist`). Marks
+ *  what the server says it moved: a video a concurrent edit already took out is in neither answer. */
+export function movePlaylistItems(qc: QueryClient, from: ListRef, ids: string[], to: ListRef) {
+  return api.moveManyToPlaylist(from.id, ids, to.id).then((r) => {
+    for (const id of [...r.moved, ...r.already_there]) {
+      markIfWatchLater(qc, from, id, false);
+      markIfWatchLater(qc, to, id, true);
+    }
+    return r;
+  });
+}
+
+/** Take a move back: every video returns to `from`, and only the ones that landed in `to` leave it;
+ *  it held the others before the move. */
+export function undoPlaylistMove(
+  qc: QueryClient,
+  from: ListRef,
+  to: ListRef,
+  back: { moved: string[]; already_there: string[]; positions: number[] },
+) {
+  return api
+    .undoPlaylistMove(from.id, to.id, back.moved, back.already_there, back.positions)
+    .then((r) => {
+      for (const id of back.moved) markIfWatchLater(qc, to, id, false);
+      for (const id of [...back.moved, ...back.already_there]) markIfWatchLater(qc, from, id, true);
+      return r;
+    });
+}